Crust: Mix salt and 2 cups flour. Rub in chopped cold butter with your fingertips. Add 4 tablespoon of cold water and roll dough into a ball. Place the dough in a plastic bag and keep it in the fridge to chill (about one hour).
Peel and chop apples into small pieces. Add sugar, cinnamon, 1/4 cup flour and 2 tablespoons cornflour. Mix well.
Remove dough from the fridge and cut it in half with a sharp knife.
Roll out half of the dough and place in in a glass baking dish. Add the apple filling. Gently, pat the 3 teaspoons butter over the apple filling. Now, roll out the other half of the dough and cover the filling completely. Dip your hands into a bowl of water and pinch the sides of the crust together. Cover the sides of the crust with aluminium foil and make decorative slits in the centre. Place it in the oven and bake for 45 minutes at 200 degrees C.