This is my favourite apple tart; buttery, rich and lemony- like a cross between crispy apple pie and Tarte Citron It is very simple and cheap to make and the great thing is, you can adjust the ingredients to suit your taste. It was named the 1x6 pie (1 apple, 1 lemon, 1 egg, 1 knob butter, 1 tablespoon of sugar, 1 pastry sheet) but I like more filling. The proportions of apples to eggs and butter should be preserved, otherwise the filling won't set. Buy the best butter puff pastry you can afford.
Heat the oven to 200C. Place the oven rack in the center of the oven.
Roll out the chilled pastry to fit a 25cm round flan tin. If you are using pre-rolled pastry sheets, fit one into the pan then cut another to fill in the spaces. Lightly dampen the edges before pressing them together to make a tight seal.
Prick the pastry, brush with the extra melted butter- this makes a layer between the wet filling and the pastry so that when the tart cooks it doesn't become soggy. Put the tart shell in the fridge while you make the filling.
Zest both lemons into a medium bowl. Add the juice of the lemons, sugar, melted butter and beaten eggs. Stir together.
Peel an apple and coarsely grate it into the egg mixture, avoid grating the core. Do the same for the other apples. Peeling one apple at a time prevents them turning brown while they sit on the bench. Stir the mixture together.
Pour the mixture into the tart shell and put it in the hot oven. Bake until the top puffs up and is dark golden brown. Puffing means the egg has set. This should take about 15-20 minutes. Don't cook it any longer than necessary but don't take it out until it has puffed up. It will sink again as it cools.
Serve in wedges at room temperature with thick cream or icecream. It can be made the day before and heated at 180C for ten minutes if that is more convenient.
I rinse the tart pan under cold water and drain it before I put the pastry in it. I learned this from a pastry chef and believe it helps the pastry crisp on the bottom. it is not a necessary step though.