Preheat the oven to 190 ° C top / bottom heat. Cover the bottom of a springform pan (28 cm diameter) with baking paper.
For the sponge cake base:
Beat the eggs, sugar, water and vanilla sugar to a very frothy cream (approx. 7-10 minutes). Carefully add the oil. Mix the flour with the baking powder, sieve and fold into the cream in portions.
Pour the batter into the springform pan, carefully smooth it out and bake for about 20 minutes. Let the bottom cool down.
For covering:
Mix the sour cream with icing sugar, spread on the cake base. Place a cake rim around it and fill in the frozen raspberries and distribute evenly. Prepare the icing with the sugar according to the instructions on the packet and pour over the raspberries. Put in a cool place for about 3 hours.