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Slow cooked onion tart

January 13, 2018
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The problem with all the cookery shows on TV (and yes I’ll admit to being glued to every season of Masterchef) is the constant striving for reinvention and novelty. In the last series of the aforementioned cookery competition, one chef who had cooked really inviting food that you would be very happy to eat as a customer in his restaurant, was often criticised for not being adventurous or inventive enough. And don’t even get me started on Great British Bake Off (who wants to eat those things?).

What’s wrong with cooking really simple things well? When you have really good ingredients often you hardly need to do much with them anyway.

Rant over and onto the start of the year and comforting food. Even in the desert where our winters aren’t really all that cold (it was 25 C today) there’s a feeling of hunkering down and getting cosy – even if it’s after you’ve just come home from the beach. KP and I have chosen to be vegetarian during January. Actually I chose and as I do most of the cooking, that’s what we’re eating!

This onion tart is all about the simple – in cooking and in taste. Putting a few things that go well together inside a case of buttery pastry.

You’ll note that the onions take a long, long, long time to cook but they don’t need much supervising. I wrote this recipe before I read this rant about onion cooking time by the way!

You can add your own twist – the bitter, melancholy flavours of rosemary or thyme go beautifully with the sweetness of the onions, whereas bright fresh herbs add a different vibe.  Stir, into the uncooked filling, a handful of grated cheddar or a softer milder cheese. Fragments of crisp bacon or spicy chorizo are other head-turners. But honestly, I take a purist line here of savouring the humble onion cooked slowly into sweet, melting submission then married with the best dairy in a crumbly case that reminds you of childhood.

A crisp, green salad is the perfect partner.

Onion tart

  • Servings: 4-6
  • Print

A simple, comforting tart made with store cupboard ingredients.


  • 50g unsalted butter, cut into small pieces
  • 100g plain flour
  • pinch of sea salt
  • 2 egg yolks
  • 1 tablespoon water (ice cold)
  • 1 tablespoon olive oil
  • 4 large onions, peeled
  • 4 egg yolks
  • 300ml double cream
  • sea salt and black pepper


  1. Make the pastry. Put the flour, salt and butter into a food processor and whizz to the texture of fine breadcrumbs. Add the egg yolks (I actually used 3  yolks as my eggs were very small if you have a very large egg you may only need one) and pulse the processor until the pastry starts to come together. Add the iced water through the tube while it is pulsing and process lightly until the dough starts to come together. Stop the processor and form the pastry into a ball. Wrap (in cling or cover in a bowl) and rest in the fridge for at least 30 minutes for the gluten to expand.
  2. Meanwhile, slice the onions finely and sauté very gently in a cast iron (or non stick) frying pan. Start them off on a higher heat and use a spatula to fold them into the oil so they are all coated and start to lose their firmness. Then turn to the lowest heat possible, stirring occasionally and until the onions are transparent and very soft. Do not let them turn darker than a very pale fawn in colour. This can take up to an hour (I often do this ahead of time in two batches).
  3. Grease a deep 20-21cm flan tin. Roll out the pastry very thinly and line the tin, gently folding it into the edge without stretching it. Prick the base with a fork and bake blind in an oven preheated to 180C for 15 minutes (or until lightly cooked through).
  4. Remove from the oven and when the tart shell has cooled a little, spread the cooked onions over the base.
  5. Measure the cream into a jug, add the eggs and beat together with a generous pinch of sea salt and lots of freshly ground black pepper. Pour the cream mixture over the onions, moving them a little with a fork to enable the liquid to sink right to the bottom.
  6. Cook in the oven for 30-40 minute, protecting the exposed edges of pastry with some strips of silver foil if they start to get too brown. Remove when the filling is lightly set and the top is starting to turn golden brown. Leave to cool a little before slicing. Serve slightly warm or at room temperature.

Onion tart and some onions

Caramelised onion tart

What simple comfort food to you turn to during the Winter?


  1. Dave Reeder permalink
    January 13, 2018 3:46 pm

    Yum, thanks for the inspiration for tomorrow’s lunch! I would have it today but kedgeree is already on the go… I’m tempted, however, just to add two or three pickled onions to the mix to give it bit more bite. And to drink with it/ something crisp and white, of course – ideal to go with the Picpoul de Pinet I just sourced from Tesco!

  2. January 13, 2018 3:50 pm

    Looks great! Caramelised onions are always worth the effort 😊

  3. January 13, 2018 3:59 pm

    One of my faves but very smelly farts! Much love.

  4. The Real Geordie Armani permalink
    January 13, 2018 5:11 pm

    I made one very similar to this recently and added leaks, was delicious. Off to watch James Martin now x

  5. January 13, 2018 8:27 pm

    Great looking tart. I agree that we need to spend more time appreciating simple dishes, well made.

  6. January 14, 2018 8:21 pm

    The versatility of onion is nothing short of amazing for me – so many dishes can be created! I have to say that I can eat even simple grilled onions by the plateful…

  7. January 15, 2018 3:27 pm

    Well said. The flamboyant stuff is fine but I love the challenge of getting something simple as close to perfect as I can. And this looks pretty damn perfect to me. And yes to slow cooked onions. Anything less than 30 minutes for a recipe that calls for slow cooked onions isn’t doing justice to this most versatile of vegetables. Lovely images, too 🙂

  8. January 16, 2018 10:24 am

    Sally I love this! And we’ve just moved to a suburb where the weekly framers market gives me access to the most amazing onions. Do you not use the egg whites at all? I noticed on yolks are on the ingredients…..

  9. Ali permalink
    February 26, 2018 11:56 pm

    My sentiments exactly. I want simple, nourishing food, using produce from our garden.

    • March 7, 2018 10:41 am

      That’s the way I was brought up and still try to get back to as much as possible.

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