Preheat oven to 180 degrees C. Grease a 23cm pie dish.
Pastry: In a large bowl, combine flours, salt and sugar. Rub or cut in butter until coarse crumbs are formed.
Mix in sour cream. Keep mixing until dough forms a ball, (dough may be slightly lumpy), this is fine. Wrap dough ball in plastic wrap and allow to chill for 1 hour.
Once chilled, take dough out of refrigerator and roll the dough to 4mm thickness. Lift pastry into the prepared pie dish. Trim overhanging edges of pie base.
Filling: Place apples into the pie base. In a small bowl, combine sugar, flour and cinnamon. Mix together thoroughly. Sprinkle mixture over apples. Sprinkle some lemon juice over apples. Place pie in refrigerator while the top is prepared.
Crumble: In a bowl, mix the flour with the salt, sugar and butter until combined, then using your fingertips rub until it resembles crumbs.
Bake in a preheated oven for 40 minutes, or until golden brown. Serve the pie warm or cold.