Preheat the oven to 175 ° C. Grease a springform pan (26 cm) and sprinkle with breadcrumbs.
Melt the butter. Wash the lemon with hot water and pat dry. Rub the peel and squeeze out the juice. Separate the eggs, beat the egg whites until stiff and let 50 g of sugar trickle in.
Mix the sour cream with 200 g sugar, vanilla sugar, egg yolks, lemon zest and lemon juice. Mix the semolina and baking powder and stir into the cream and egg mixture with the melted butter.
Fold in the egg whites, pour the batter into the springform pan and bake for about 35 minutes. Then dust with powdered sugar.