Cut the rolls into thin slices. Distribute on a baking tin and toast slightly in the oven at 120°C. Melt butter and dripple over the rolls occasionally. Remove the rolls and increase the heat to 180°C. Blend the eggs with sugar, vanilla sugar, salt, milk and lemon peel. Butter an oblonb casserole dish (approximately 1.5l). Put 1/2 of the sliced rolls into the dish and pour 1/2 of the egg milk over them. Peel and core the apples, cut into thin slices and mix with the cinnamon and rum. Sprinkle the raisins onto the rolls and cover with the apple slices. Cover with remaining roll slices and pour of the rest of the egg milk over everything. Distribute the knobs of butter on the surface and bake in the oven for approximatley 45 minutes until golden brown. Sprinkle with icing sugar and serve immediately.