Preheat oven to 180 C / Gas 4. Lightly grease a tart tin.
To make the pastry: Combine flour with softened butter, icing sugar, water and salt; mix with your hands until it forms a smooth dough. Divide the pastry into two parts: one slightly larger amount to fit the base of the tart tin, the other to form a thinner layer of pastry for the top.
Roll out the larger part of the pastry and transfer it into prepared tart tin. Prick with fork in several places and bake in preheated oven for 30 minutes.
For the filling: Mix the grated apples with cinnamon and set aside.
Roll out the second part of the dough to cover the top of the pie.
Once the base is baked, spoon the apple and cinnamon mixture on top of the base; cover with the second layer of pastry. Prick with a fork in several places and bake for 40 minutes. Cool slightly on a wire rack.
Once the pie has cooled a little, sprinkle generously with icing sugar. Serve warm with ice cream or whipped cream.