Peel and dice the apples and marinate with the rum.
Mix the butter with sugar and egg yolk until foamy, add the vanilla pulp.
Mix the flour with the baking powder, hazelnuts, cocoa and cinnamon and stir into the frothy egg mixture, as well as the prepared apples. Beat the egg whites, sugar and salt until stiff, and carefully fold the egg whites into the batter. Pour the mixture into a greased loaf pan sprinkled with breadcrumbs.
Bake in a preheated oven at 175 ° C top / bottom heat for 1 - 1.5 hours. After baking, let the cake cool down and turn it out of the tin.