For the yeast dough, put the hot milk in a mixing bowl and swirl so that the bowl warms up. Dissolve the sugar and softened butter in the milk. Add the grated lemon zest and 1 egg. (Can no longer be hot, but only lukewarm.) Then crumble in 1 cube of yeast and stir in.
Gradually stir in 500 g flour and a pinch of salt. Dust with flour, cover with a kitchen towel and let rise in a warm place for 20-30 minutes.
For the topping, mix together sour cream, vanilla sugar and sugar. Mix 2 teaspoons of cornstarch with a little milk and add.
Remove 1/3 of the yeast dough and roll it out on a greased round brook tray with a rim of approx. 28 - 30 cm. Then distribute the topping on it. Sprinkle with cinnamon and sprinkle small flakes of butter on top.
Preheat the oven to 180 ° C with hot air and bake the cake for 25-30 minutes. Then take the cake out and let it stand for about 15 minutes, only then remove it from the baking sheet and place on a wire rack to cool down.
You can make 2 cakes from the rest of the yeast dough, or freeze them for the next time.