For the pastry
Sift the flour into a mixing bowl.
Add the cubes of butter and rub in.
Sprinkle over the cold water and mix in with the a fork to moisten the mixture evenly.
Now draw the mixture together with your fingertips to make a dough.
Tip it onto a floured surface and gently knead into a ball.
Cover and rest for 10 minutes.
Then roll it out and line the tart tin. Prick the base all over with a fork and chill the pastry case while preparing the filling.
For the filling
First preheat the oven to 190°C (375°F) (Gas 5) and place a baking sheet in the oven while it is heating up.
Peel, core and cut the apples into small chunks. Put into a pan.
Zest the lemon and then squeeze out the juice. Add to the pan.
Set over a low heat, cover, and let the apples stew gentle for about 15 minutes, until they are soft. Stir occasionally.
Remove from the heat and beat the apple vigorously to produce a purée.
Now add the sugar and butter and stir until they have melted.
Then beat in the egg yolks.
Pour into the pastry case and place it on the hot baking sheet. Bake for 25–30 minutes, until the pastry is golden.
Remove the baking sheet and tart from the oven and put to one side while preparing the meringue.
For the meringue
First reduce the oven temperature to 150°C (300°F) (Gas 2).
Then whisk the egg whites until stiff.
Gradually add the sugar, one tablespoon at a time, whisking well between each addition, until the meringue is stiff and glossy.
Pile the meringue on top of the apple, making sure it completely covers the filling, and pull the meringue up into peaks using the tip of a knife.
Bake for 15–20 minutes, until the meringue is golden.
Allow the tart to cool in the tin and serve at room temperature.