Peel the apples, quarter them, remove the core and cut into cubes. Mix with sugar, vanilla sugar and lemon juice and spread in a buttered casserole dish.
For the crumble, knead the flour with the ground almonds, sugar and butter and rub between the palms of your hands to make crumble. Spread on the apples and bake in the preheated oven for 25-30 minutes.
Take out, let cool down lukewarm and serve with whipped cream or vanilla ice cream, if you like.