Peel the apples, cut them into cubes, add sugar and pour the juice of a lemon over them. Mix everything well. Line a 26 cm springform pan with baking paper and grease the edge. Preheat oven to 180 ° C O / U heat.
Roast the chopped hazelnuts in a coated pan without fat and set aside. Mix the flour, sugar, cinnamon, vanilla flavor and chopped hazelnuts together. Melt the butter and mix it with the dry ingredients to make crumble, it's quick and easy with your hands.
Put the ingredients for the dough in a bowl and stir to form a smooth dough.
Pour the dough into the springform pan and smooth it out. Spread the apple pieces on top, but without the juice that has collected in the bowl in the meantime. Then spread the prepared nut crumbles over the apples. I immediately found a sweet tooth for the last pieces of apple.
Bake the cake in the preheated oven for about 40 minutes. Then let cool on a wire rack.