Mix the softened butter with the eggs, sugar, vanilla sugar, cinnamon, rum and yogurt. Add the flour, baking powder and baking soda, mix everything into a batter.
Add walnuts and raisins. Peel, core and roughly cut the apples. Drizzle with lemon juice and stir into the batter.
Spread on a small baking sheet lined with baking paper. Bake at 200 ° C for approx. 45 - 50 minutes. Allow to cool, dust with icing sugar.