Cream 113 g (1/2 cup) butter, sugar, and vanilla sugar (or extract) thoroughly.
Add eggs one at a time.
In a seperate bowl: mix flour, baking powder, and baking soda together.
Add to batter mixture alternately with the sour cream, blending after each addition.
Spread batter in a 22cm/9″ springform pan that has been buttered and lightly floured.
Top with cranberries, pressing the berries down slightly into the batter.
Sprinkle streusel mixture evenly over batter, pressing down slightly into batter.
Bake at 180C/350F degrees 50-60 minutes, until golden brown.
Cool completely on a wire rack.