Take the lid off the onions and raise the heat slightly for the last 10 minutes, I don't like them too dark and sweet, but you can carry on until they're really caramelised if you want to. When they're sweet and sticky add a knob of butter and a dash of white wine vinegar.

Preheat the oven to 180C/Gas 4. Unroll the sheet of pastry and trim all the edges very thinly, this helps the layers of pastry to rise. Place on a baking tray and use a sharp knife to cut a border all the way round for the crust. Don't cut all the way through.

Cook the pastry until puffed up and golden, about 15 minutes. Remove from the oven and straight away cut through the marked out border.

Then push the puffed up centre down to form a raised edge and indented middle.

Spread the caramelized onions over the base, then crumble over the feta cheese. Scatter the chopped oregano over.

Add the tomato slices then drizzle the egg and cheese mixture into the tart and add some more black pepper. Cook in the oven for about 20-25 minutes until the cheese topping is golden and the tomatoes are cooked.

Eat the tart warm with a big leafy salad. We ate the whole thing between 2 of us, but it would serve 3 or even 4 if you serve with sauteed potatoes and more salad.