Sieve the flour with the baking powder. Add the sugar, vanilla sugar, eggs, sour cream and the softened butter and stir to a smooth batter. Divide the dough into 4 - 5 portions and color them vigorously with food coloring.
Alternately blob the colorful dough onto a baking sheet lined with baking paper, drive a fork vigorously through the mass and knock the sheet several times on a solid surface (table top) so that everything connects properly and air holes are knocked out.
Bake the cake on the middle rack at 170 ° C for 30 minutes. After the cake has cooled, cover with icing and garnish with colorful sprinkles.