Preheat the oven to 170 degrees top / bottom heat.
Grease 6 small casserole dishes with butter. Peel the apples. Drizzle with lemon juice to prevent the apples from turning brown in the meantime.
Mix the butter, sugar, eggs and vanilla sugar until frothy. Fold the flour, baking powder, cinnamon and nuts into the mixture. Stir the dough until the flour is well mixed with the dough.
Fill the greased casserole dishes two-thirds full with batter. Place a small apple in each mold and bake on the middle rack for about 30 minutes until golden brown.
Let the baked apple dessert cool down a little and sprinkle with powdered sugar before serving.