For the yeast dough mix 400 g flour, 50 g sugar, 1 pinch of cinnamon and 1 pinch of salt in a mixing bowl. Press a depression in the middle. Warm up about 5 tablespoons of buttermilk lukewarm. Crumble yeast into it and dissolve it.
Pour the aroma into the bowl and mix with some of the flour to make the pre-dough. Cover and leave to rise in a warm place for about 15 minutes.
Add the egg, 1⁄4 l buttermilk and 60 g butter in flakes to the pre-dough. Knead everything smooth with the hand mixer. Cover and leave to rise for about 30 minutes.
For the crumbles, melt 275 g butter over a low heat. Mix 500 g flour, 250 g sugar, 1 pinch cinnamon and 1 pinch salt. Slowly stir in the butter and use the dough hooks of the hand mixer to make crumbles.
Grease a fat pan (approx. 32 x 39 cm; at least 3.5 cm deep) and dust with flour. Knead the yeast dough again, dust with a little flour and roll out on the fat pan. Cover and leave to rise for about 15 minutes.
Spread crumble on top.
Bake the cake in a preheated oven (electric oven: 200 °C/circulating air: 175 °C/gas: see manufacturer) for approx. 15 minutes. Sprinkle with remaining buttermilk and bake for about 15 minutes. Let it cool down.
Sweetened strawberries and whipped cream taste great with it.