Preheat the oven to 160C. Grease a deep loose bottom 8-inch cake tin or a large plate.
In a large bowl, with a wooden spoon or an electric mixer, beat 125g butter and icing sugar until creamy. Stir in the egg. sieve the flour over and combine the flour with the mixture to form pastry dough. Shape in a rectangular shape and wrap in Clingfilm. Allow to rest for at least 30 minutes.
In the meantime, combine the pitted cherries, apple, lemon zest and juice, the rest of the butter ( 50g), brown sugar and corn flour in a bowl. Set aside to marinate for 10-15 minutes.
Next, remove the pastry from the refrigerator. Divide the pastry into 2 pieces and roll the first ball out to line the base of the tin. Brush the edges with egg wash to help seal at a later stage.
Add the cherry mixture including the juices if any in the pastry.
Roll the second part of the pastry and carefully place it over the cherry mixture.
Seal gently pressing the edges. And clear excess pastry hanging around the edges with a knife if needed.
Brush the pastry with some more egg wash and sprinkle some extra brown sugar over.
Place in the oven and bake for 40-50 minutes until golden brown colour and cooked through.
Remove the pie from the oven and set aside for 20 minutes to cool.
Serve with your favourite ice cream or fresh cream.