Separate the eggs. Beat the egg whites with the salt until stiff. Possibly put in the refrigerator.
Mix the butter, sugar and egg yolks well, then stir in the low-fat quark. Mix the flour with semolina and baking powder and fold into the mass. Now add the egg white.
Put the mixture in a round baking pan (26 - 28 cm) that has been greased or lined with baking paper. Spread the blueberries on the batter.
Knead the ingredients for the crumble and distribute as a crumble on the blueberries. Bake the cake in the preheated oven for about 30 minutes at 180 ° C (top / bottom heat).