For the pastry:
225g plain flour
125g butter, cubed
1 egg, beaten
1 tbsp water
For the filling:
500g onions, thinly sliced
A knob of butter
1 tbsp olive oil
4 large eggs
300ml double cream
200g gruyere, grated
30g parmesan, grated
1 Line a 9.5-10 inch deep round loose bottom tart tin.
2 To make the pastry, put the flour, butter and cheese into a food processor. Whizz until it looks like breadcrumbs. Add the egg and water and whiz until the mixture forms a ball.
3 Roll out on a lightly floured work surface and line the base and sides of the flan tin with the pastry. Set aside to chill in the fridge for 30-35 minutes. Prick the base and line with baking beans.
4 Pre-heat the oven to 220C / 200C Fan / Gas mark 7. Blind bake the pastry for 10 minutes. Remove the beans and bake for another 8-10 minutes until lightly golden. Place on a baking sheet.
5 To make the filling. Melt the butter and oil in a frying pan. Add the onions and fry over a medium to high heat for 5 minutes. Cover with a lid and gently simmer for 20 minutes until soft and golden brown. Spread onto the base of the tart.
6 Beat the eggs in a bowl. Add the cream and milk and season. Add the gruyere cheese, then pour into the case. Sprinkle with the parmesan.
7 Reduce the oven to 180C / 160C Fan / Gas mark 4. Bake for 30-35 minutes until lightly golden on top and set in the middle.
Annabel’s Family Cookbook (£20, Ebury Press) is filled with cooking inspiration for the whole family and available to buy from 13 March. Visit www.annabelkarmel.com
Don't miss... our Q&A with Annabel and her recipe for roasted chicken with sweet peppers
Have you seen... Annabel Karmel's delicious lunchbox suggestions?
Did you know... the New Complete Baby & Toddler Meal Planner by Annabel Karmel was highly Commended in the Junior Design Awards 2012?