Separate eggs. Mix the egg yolks with the sugar until frothy. Melt the margarine. Mix the flour and baking powder and add to the egg mixture with the margarine. Beat egg whites until stiff and fold in.
Line a baking sheet with parchment paper and spread the batter on it.
Streusel:
Mix the butter and sugar, then add the remaining ingredients and knead until a crumble dough is formed. Shape it into balls and distribute them individually on the dough, do not press in, as the light-colored dough still rises during baking and slightly covers the crumble.
Bake at 180 degrees top / bottom heat for 25 minutes.