Peel and core the apples then cut them into small chunks.
Fry them in a large pan with butter, sugar and cinnamon until fragrant and softened but still holding their shape approx 15-20 min. Set aside.
Sieve the flour and baking powder together, add sugar and butter. Rub all the ingredients in together with your fingers or using food processor until you get consistency of fine breadcrumbs. Add one egg and the egg yolks and knead or process in the processor until the dough comes together.
Divide the dough into two, cover in cling film and put one half in the fridge and another one in the freezer for about an hour.
Line bottom of the cake tin with baking paper. Take half of your pastry out of the fridge and grate over the bottom of the tin pressing it in with your fingers and flattening it lightly (you can also roll the dough out to fit your tin but I find my method easier). Put the tin lined with pastry in the fridge.
Whisk the egg whites until stiff and then slowly start adding sugar while still whisking. At the very end add the cornflour and whisk a bit more until incorporated. You will get nice and shiny meringue.
Take the cake tin out of the fridge. Put the apples on top of the pastry and follow with the meringue which you spread gently and evenly over the apples.
Take another half of the pastry out of the freezer and grate over the top of the meringue. You might not need to use the whole lot for the top, it all depends on how thick would you like your top pastry layer to be.
Bake at 180C for an hour. After half an hour of baking cover the top of your pie gently with a piece of aluminium foil to prevent it from browning too much.
Cool slightly and sprinkle with icing sugar. Serve with some delicious vanilla ice cream or lashings of custard.