Recipe of the week: Tomato, onion and cheddar tart

The pastry for this tart is a bit different, says Danielle Alvarez: it incorporates both butter and sour cream and it just makes the most delicious, delicate, flaky, buttery tart you’ve ever tasted. The recipe is inspired by my friend Martin, who made a version of this tart at a lunch we were cooking at. He told me it was his grandmother’s recipe, which didn’t surprise me: it’s old-fashioned and I love it.

Serves 6-8 Leafy salad, to serve for the pastry: 250g plain flour, plus extra for dusting 150g cold unsalted butter, diced

½ tsp salt 125g sour cream 1 egg for the filling: 300g large heirloom tomatoes (approx. 1-2) 400g white onion, thinly sliced 2 tsp chopped thyme 50g unsalted butter 100g sour cream 100g grated cheddar cheese 3 eggs 1 tbsp plain flour 2 tbsp cream

2 tbsp grated Parmesan salt and black pepper to season

• Make your pastry: Combine the flour, butter and salt in a food processor and pulse until it resembles fine crumbs. Add the sour cream and egg and pulse a few more times until the pastry comes together in a ball. Shape into a disc, wrap in cling film and chill for at least 1 hour in the fridge.

• Preheat the oven to 180°C. Dust the pastry with flour and roll out to a 2-3mm thickness (try to keep it round). Line a 23-25cm pie dish or tart tin, leaving 1-2cm of excess pastry hanging over the edge to allow for shrinkage as it bakes. Use scissors to trim off any wider bits.

• Lay a sheet of baking paper on top of the pastry and fill with baking weights or uncooked rice or beans to prevent the pastry puffing up. Place the dish on a tray and bake for 20-30 mins. When the crust is looking golden on the edges, remove the baking weights and bake for a further 15-20 mins. If the crust looks like it’s puffing up, poke a few holes in it to allow steam to escape. When golden, remove from the oven and leave to cool. Reduce the temperature to 160°C.

• Peel your tomatoes by cutting a small X on their base, dropping them into boiling water for 10-20 seconds, then immediately refreshing in iced water. The skin should peel off easily, starting vfrom the X. Cut into 5mm slices. Set aside. In a sauté pan, sauté your onions and thyme in the butter until soft and translucent but not coloured. Season and set aside to cool. Once cool, mix with the sour cream, cheddar, eggs and flour.

• Pour the mixture into the tart shell, then layer the sliced tomatoes over the top. Sprinkle over the cream and Parmesan and place on a tray. Bake for 40-60 mins, until the tart is completely set. If the crust is browning too much, wrap the edge in foil to allow the custard to continue cooking. Serve warm or at room temperature with a salad.

Taken from Always Add Lemon by Danielle Alvarez, published by Hardie Grant at £26. To buy from The Week Bookshop for £20.99, call 020-3176 3835 or visit theweekbookshop.co.uk.