Cheesy Caramelized Onion Tart with Homemade Pastry

To make the pastry, combine the flour and cold cubed butter in a large bowl. Rub the mixture together with your fingertips until it resembles coarse breadcrumbs. Add the beaten egg and mix with your hands until the dough just comes together. Shape into a disc, wrap in plastic, and chill for at least 30 minutes (or freeze for up to a month).

On a lightly floured surface, roll the pastry out into a circle roughly 28cm in diameter. Carefully lift the pastry using a rolling pin and drape it over a 23cm tart tin. Use a small ball of pastry scraps to gently press the dough into the base and up the sides, allowing the excess to overhang. Chill in the fridge for another 20 minutes.

While the pastry chills, melt 50g of butter in a pan over low-medium heat. Add the sliced onions and cook for about 45 minutes, stirring occasionally, until they are golden, sticky, and caramelized. Season generously with salt, stir in the double cream and nutmeg, and bring to a gentle simmer before removing from the heat.

Preheat your oven to 200°C (180°C fan/gas 6). Lightly prick the base of the chilled tart shell with a fork. Line with baking parchment and fill with baking beans or rice. Blind bake for 20 minutes, then remove the beans and parchment and bake for an additional 10-15 minutes until the pastry is light brown and cooked through.