Cake: Mix the butter and brown sugar, then add sifted flour, cornflour and baking powder. Finally add the eggs, vanilla and lemon flavour. Spread mixture in a greased spring form (24-26 cm). Spread diced apples over the base in the spring form.
Crumble: Mix butter, sugar, flour and vanilla to crumbles then spread over apples.
Bake 40 to 45 minutes at 160 degrees C (fan forced).