Ingredients

200g plain flour, plus extra for dusting

100g cold butter, cubed, plus 25g

150g gruyère, comté or vegetarian Italian-style hard cheese, grated

Small handful of thyme, leaves picked

1 tbsp olive oil

3 large onions, finely sliced

2 tbsp white wine or sherry vinegar

1 tbsp sugar

2 brown anchovies, finely chopped, or 1 tsp olive tapenade or umami paste

2 large eggs

300ml double cream

1 tbsp extra virgin olive oil

2 tsp balsamic vinegar

2 sundried tomatoes, finely sliced

6-8 pitted black olives, thinly sliced

1 tsp capers

A few handfuls of rocket

Instructions

Step 1: Put the flour in the bowl of a food processor with 100g cold butter. Blitz until the mixture looks like fine breadcrumbs. Add 50g cheese, 1 tbsp thyme leaves, freshly ground black pepper, and 1 tsp salt. Blitz briefly to combine. Add 2-3 tbsp cold water and pulse until it forms a dough. Alternatively, rub the flour into the butter in a bowl, then stir in the other ingredients. Wrap the dough and chill for at least 40 minutes.

Step 2: Heat 25g butter and 1 tbsp olive oil in a large frying pan over low-medium heat. Cook the sliced onions with a pinch of salt for 40–50 minutes, stirring often, until they are sticky, golden, and very soft. If they start to catch, reduce heat and add a splash of water to prevent burning.

Step 3: Stir in the vinegar, sugar, and anchovies (or tapenade/umami paste). Keep stirring until the vinegar evaporates and anchovies dissolve into the onions. Remove from heat.

Step 4: Preheat the oven to 190°C (170°C fan)/gas mark 5. Roll out the pastry on a lightly floured surface to about 3mm thickness. Line a 23cm tart tin with the pastry, trimming the edges to slightly overhang. Patch any holes with offcuts. Line the pastry with scrunched then flattened baking parchment and fill with baking beans. Bake for 15 minutes.

Step 5: Remove the parchment and beans, then bake for another 5–8 minutes until the pastry looks dry and free of raw spots.

Step 6: Whisk eggs, double cream, remaining thyme, remaining cheese, salt, and pepper in a bowl. Stir in the caramelized onions. Trim the edges of the pastry with a serrated knife for a neat finish. Pour filling into the pastry case and gently tap the tin to release air bubbles.

Step 7: Bake the tart for 25–30 minutes on the middle shelf until lightly golden and mostly set but still slightly wobbly in the center. Let cool in the tin for 15–20 minutes before slicing.

Step 8: For the salad, whisk olive oil and balsamic vinegar together. Toss in sundried tomatoes, olives, capers, and rocket. Serve the salad either on top of or alongside the tart. The tart can be served warm or chilled, and keeps in the fridge for up to three days.

Tips & Variations

Use vegetarian cheese and skip anchovies for a fully vegetarian version; umami paste adds depth of flavor as a substitute.

Take your time caramelizing the onions; patience ensures deep, rich flavor.

For extra crunch, sprinkle some toasted nuts or seeds on the salad.

Serve with a crisp white wine or a light red to complement the rich tart.

FAQs

Can I make the pastry ahead of time?

Yes, the pastry dough can be made up to 24 hours in advance. Keep it wrapped and chilled until ready to use.

What cheese works best for this tart?

Gruyère, comté, or a vegetarian Italian-style hard cheese work well. They melt nicely and add a nutty, savory flavor that complements the caramelized onions.