Marble Cake with Poppy Seeds

Preheat the oven to 150 °C fan (170 °C top/bottom heat).

Grease a bundt pan thoroughly and sprinkle with breadcrumbs.

Separate the eggs and beat the egg whites with a pinch of salt until stiff.

Cream the butter, sugar and vanilla sugar until fluffy.

Gradually beat in the egg yolks, then fold in the lemon yogurt.

Mix the flour and baking powder and briefly stir into the egg mixture, only until no dry flour is visible.

Gently fold the egg whites in 2–3 additions.

Pour about 3/4 of the light batter into the pan. Stir the poppy seed filling into the remaining batter and spoon it over the light batter.

Bake the cake for about 45 minutes, then perform a skewer test.

Remove the cake from the oven, let it cool briefly in the pan, then invert onto a wire rack and cool completely.

Dust with powdered sugar if desired and serve.