This post is sponsored by Sullivan's Greengrocers. This post also contains affiliate links and if you make a purchase through one of these links, I'll receive a modest commission fee at no extra cost you.
This traditional Welsh onion cake recipe combines layers of potatoes and onions with leeks, thyme and mature Cheddar for a subtle flavour boost. Costing less than £1 per serving, it’s an easy, affordable and comforting dish with a crisp, golden top and buttery, tender layers beneath.
If you asked my family to name their favourite traditional Welsh dishes, Welsh onion cake would almost certainly make the list. Whether it’s served alongside a roast dinner or simply enjoyed with a crisp green salad, it’s one of those comforting recipes that never seems to lose its appeal.
What is Welsh onion cake?
Despite what the name might suggest, Welsh onion cake isn’t a cake in the way we usually think of one. Known in Welsh as teisen nionod – and sometimes teisen winwns or even cacen nionod, depending where in Wales you are – it’s a simple yet satisfying savoury bake made by layering thinly sliced potatoes and onions with butter, seasoning and, in some versions, a little cheese before baking until crisp and golden.
If you’re wondering about the name, there’s another surprise. The dish doesn’t traditionally contain Welsh onions – a perennial onion that looks rather like a spring onion. Instead, it’s made with ordinary bulb onions, with the name simply reflecting the recipe’s roots in Wales.
Although its exact origins have been lost to time, Welsh onion cake reflects the resourceful cooking of Welsh households, transforming affordable staples such as potatoes, onions and butter into a hearty, comforting dish that has endured for generations.
If you’re familiar with French cooking, Welsh onion cake bears some resemblance to pommes boulangère, with its layers of potatoes and onions baked until golden. Unlike the French classic, however, it isn’t cooked with stock and often includes cheese, giving it a richer, distinctly Welsh character.
My take on traditional Welsh onion cake
Traditional Welsh onion cake relies on just a handful of ingredients, but this version gives the classic recipe a subtle lift without losing its character. Alongside the customary potatoes and onions, I’ve added thinly sliced leeks, fresh thyme and a scattering of mature Cheddar, creating extra layers of flavour while keeping the dish firmly rooted in Welsh cooking.
Some traditional recipes omit the cheese altogether, while others use crumbly Caerphilly cheese for a tangier finish. Feel free to experiment, but I love the richness that mature Cheddar brings to the finished bake. I’m also keen to try making Welsh onion cake with blue cheese.
Why you’ll love my Welsh onion cake recipe
One of the things I love most about Welsh onion cake is how economical it is to make. Costing less than £1 per serving, it’s a fantastic way to transform a few everyday ingredients into something comforting enough for a Sunday lunch or special family meal.
It’s wonderfully versatile too. Serve it alongside roast lamb, beef, pork or chicken with plenty of gravy, or enjoy a generous slice with a crisp green salad for a simple vegetarian lunch or supper.
As well as being affordable, the ingredients offer plenty of nutritional value. Potatoes provide fibre, vitamin C and potassium, while onions and leeks are rich in antioxidants and prebiotic fibre, which supports a healthy gut. Fresh thyme contributes both flavour and natural plant compounds, and using good-quality, seasonal vegetables – fresh, good-quality, seasonal vegetables – helps maximise both flavour and nutritional value.
The best ingredients for Welsh onion cake
Recipes like this rely on only a handful of ingredients, so their quality really matters. For this recipe, I sourced my vegetables from Sullivan’s Greengrocers, a family-run independent business that has been trading from Cardiff Market for decades.
As well as serving customers in the historic market, they deliver fresh fruit and vegetables throughout Cardiff and the Vale of Glamorgan, making it easy to enjoy high-quality produce without leaving home. Alongside fresh produce, they stock a range of everyday essentials, including milk, cheese, eggs and other dairy products, meaning you can often pick up everything you need for a recipe in one order. Sullivan’s also supply many of the region’s leading restaurants, cafés and hospitality businesses.
Choosing an independent greengrocer isn’t just good for your cooking. It also helps support local businesses, keeps more money within the local economy and often reduces unnecessary plastic packaging compared with buying pre-packed supermarket produce.
Sullivan’s offer a range of seasonal fruit and vegetable boxes, or you can create your own bespoke order to suit your needs. Browse their range of fruit and veg boxes here.
How to make Welsh onion cake to an authentic Welsh recipe
Traditional Welsh Onion Cake (Teisen Nionod)
Equipment
- 1 mandolin optional
- 1 cut-resistant gloves optional
Ingredients
- 3 medium onions approx. 300g, peeled
- 700 g Red, Désirée or Maris Piper potatoes peeled
- 1 large leek approx. 150g washed, trimmed and halved lengthways
- 100 g unsalted butter melted, plus 1 tbsp melted butter for brushing
- 150g g mature Cheddar grated
- 2 tsp fresh thyme leaves
- salt and pepper to season
Instructions
- Preheat the oven to 220°C / 200°C fan/Gas Mark 6.
- Slice the onions, potatoes and leeks into 2-3mm rounds using a mandoline or a sharp knife.
- Grease a deep 23-24cm round pie dish or cake tin.
- Toss the potato slices with most of the melted butter until lightly coated, reserving some for basting and pouring over the top.
- Arrange a layer of potato slices over the base, and season lightly with salt and pepper. then top with some of the onions and leeks. Add another light seasoning, a scattering of Cheddar and a few thyme leaves. Repeat the layers until all the ingredients have been used, finishing with a layer of potatoes.Press down gently on each layer as you build the onion cake to help create neat, compact layers.
- Top with some of the onions…
- … followed by a layer of leeks.
- Add a scattering of Cheddar and a few thyme leaves.
- Repeat the layers until all the ingredients have been used, finishing with a layer of potatoes. Season with salt and pepper. Press down gently on each layer as you build the onion cake to help create neat, compact layers.
- Brush the final potato layer with melted butter, and pour any remaining melted butter into the dish. Cover with foil, and bake for 1 hour.
- Remove the foil and brush the surface with the remaining tablespoon of melted butter. Reduce the oven temperature to 200°C / 180°C fan/Gas Mark 6. Return to the oven for 30 minutes more, or until the potatoes are completely tender and the top is crisp and deeply golden.
- Leave to rest for 10 minutes before garnishing with a few extra thyme leaves. Serve warm with a lightly dressed salad as a main meal, or with roast meats or sausages as a side dish.
Notes
- Slicing the veg: You can use a sharp knife to slice the potatoes, leeks and onions, but a mandoline will produce the most even slice – just be sure to use the safety guard, and consider wearing cut-resistant gloves for added protection.
- Potatoes: Désirée potatoes hold their shape well while becoming beautifully soft, although Maris Piper and Red potatoes also work well.
- Cheese: Mature Cheddar adds a rich savoury flavour without overwhelming the potatoes and onions. For a more traditional Welsh twist, try replacing some or all of it with Caerphilly cheese. Alternatively, omit the cheese altogether for a lighter, more traditional approach.
- Servings: This recipe produces four generous servings to be eaten as part of a main meal, or six smaller slices to enjoy alongside a main meal.
- To reheat: To reheat the whole onion cake, cover it with foil and place it on a baking tray in an oven preheated to 170°C fan / 190°C / 375°F / Gas Mark 5 for 20-25 minutes, or until piping hot throughout. Remove the foil for the final 5 minutes to help restore the crisp, golden top. For individual slices, reheat in the same oven for 10-15 minutes, or in an air fryer at 180°C for 8-10 minutes, checking occasionally to prevent over-browning.
- Storage: Allow the Welsh onion cake to cool completely, then cover and refrigerate for up to 3 days. It can also be frozen for up to 3 months. Defrost overnight in the fridge before reheating.
Nutrition
Variations
Like many traditional recipes, Welsh onion cake varies from household to household.
- Some recipes recommend softening the onions or leeks in butter before layering them into the dish. I prefer to skip this step, as very thin slices soften beautifully in the oven, particularly when cut using a mandoline. If you’re slicing the vegetables by hand and they’re a little thicker, lightly cooking them first may help them become tender.
- You’ll also find recipes that add a splash of vegetable or meat stock for extra richness, although I don’t think it’s essential. Herbs are another area where cooks differ. Some omit them altogether, while others use parsley or chives in place of thyme.
- Although the traditional recipe doesn’t include leeks, herbs or Cheddar, many Welsh cooks enjoy adding their own twist. If you’d prefer something closer to the classic, simply leave them out or replace the Cheddar with a light scattering of crumbly Caerphilly cheese. Feel free to experiment with different herbs – thyme, rosemary and chives work well.
- This recipe can easily be adapted for different dietary needs. For a vegetarian version, use a cheese made with non-animal rennet, such as Snowdonia Cheese Company’s Black Bomber or Caws Cenarth’s Caerffili. To make it vegan, replace the butter with a good-quality vegan butter or olive oil and use your favourite plant-based cheese. For a dairy-free version, substitute the butter with a dairy-free spread or olive oil and use a dairy-free cheese alternative, or simply omit the cheese altogether.
What to serve with Welsh Onion Cake
Welsh onion cake is wonderfully versatile and can be enjoyed as a side dish, light lunch, or part of a hearty dinner. Equally delicious enjoyed warm from the oven or at room temperature as part of a picnic or buffet spread, it pairs beautifully with roasted meats like lamb, beef, or chicken, while its buttery potato layers also complement sausages and bacon.
For a lighter meal during the summer months, serve it alongside a crisp green salad dressed with olive oil. If you’re particularly peckish, you could team it with some cold cooked meats like ham or roast chicken. I’ve opted for a simple salad of seasonal leaves with heritage tomatoes and spring onions drizzled with olive oil, seasoned with salt and pepper, and garnished with edible flowers (all available from Sullivan’s Greengrocers).
How to store Welsh onion cake
If you somehow don’t manage to polish it all off in one sitting, Welsh onion cake keeps well in the fridge for a few days and reheats beautifully in the oven, making it an excellent make-ahead lunch or side dish.
Allow it to cool completely before transferring it to an airtight container, where it’ll keep in the fridge for up to four days. It also freezes well for up to three months. Defrost overnight in the refrigerator before reheating.
To reheat, cover the onion cake with foil and place it on a baking tray in an oven preheated to 170°C for around 20-25 minutes or until piping hot throughout, uncovering for the final five minutes to crisp it up again. Alternatively, reheat slices in an air fryer at 180°C for 8-10 minutes, checking occasionally to prevent over-browning.
Where to buy your ingredients
As this recipe uses so few ingredients, good-quality produce makes all the difference. Sullivan’s Greengrocers stock a fantastic range of fresh, seasonal fruit and vegetables, available to buy in Cardiff Market or delivered throughout Cardiff and the Vale of Glamorgan. Browse their fruit and vegetable box range or create your own bespoke order at CardiffGreengrocer.com.
If you’d like to make this recipe yourself, Sullivans also offers a convenient Welsh Onion Cake Recipe Box containing the ingredients you’ll need.
More Welsh food we love
If you enjoyed this Welsh onion cake recipe, why not try some of my other favourite traditional Welsh dishes?
- Bara brith (Welsh fruit loaf)
- Corned beef rissoles
- Crempogau (Welsh pancakes)
- Gammon cawl
- Glamorgan sausages
- Lavercakes (with Welsh Laverbread)
- Welsh cakes
- Welsh mussels and whisky
- Welsh Porc faggots
- Welsh rarebit
Have you ever tried traditional Welsh onion cake, or do you have your own family recipe for teisen nionod? I’d love to hear how you make yours – let me know in the comments below.
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This post is sponsored by Sullivan's Greengrocers. This post also contains affiliate links and if you make a purchase through one of these links, I'll receive a modest commission fee at no extra cost you.
This looks absolutely delicious! I love how a few simple, affordable ingredients can come together to create such a comforting dish. The addition of leeks, thyme, and mature Cheddar sounds like the perfect way to add extra depth of flavor while still keeping the recipe true to its traditional roots. Definitely adding this to my list of recipes to try—thanks for sharing!
Thanks Joshep – hope you love this recipe as much as I do 🙂