Place the flour in a medium bowl and use your fingers to rub the butter through until the mixture resembles fine bread crumbs.

Add the egg yolk and lemon juice and mix to form a dough.

Shape it into a ball then press to a disc, wrap in plastic wrap and refrigerate for at least 30 minutes.

Grease and line a 30x10cm loose-bottom quiche dish.

Pre-heat the oven to 175C (347F) fan-forced.

Flour the bench and roll out the dough to about 3mm thick and long and wide enough to cover the tin.

Press the dough into the tin and trim the edges.

Prick the base all over with a fork.

Cover with a sheet of baking paper and weigh down with pie weights, dried beans or rice.

Bake for 10 minutes then remove the weights and bake a further 10 minutes.

Increase the oven temperature to 180C(356F) fan-forced.

Heat the oil in a medium frying pan and saute the onion until soft.

In a medium bowl, combine all the filling ingredients then spread into the pastry.

Bake for 30 minutes or until firm in the middle.