For the poppy seed yogurt cake, sift flour with baking powder.
Separate egg whites from yolks. Beat egg whites until stiff peaks form. Beat yolks with a mixer until foamy. Then successively stir in sugar, vanilla sugar, yogurt, oil. Mix in flour and then the poppy seeds.
Finally, carefully fold in the beaten egg white.
Grease a cake pan with a diameter of 26 centimeters with butter and dust with flour. In the meantime, preheat the oven to 180 °C. Bake the poppy seed yogurt cake on the middle shelf at 180°C top and bottom heat for about 60 minutes.