Warm the milk and dissolve the yeast in it and let it rise for a few minutes.
Mix the flour with the salt, add the yeast milk and the softened butter and work everything into a smooth dough. Then let it go for about 30 minutes until it has enlarged significantly (I always do this in the BBA).
In the meantime, peel the onions, cut in half and cut into rings.
Fry the bacon or ham cubes in the butter, add the onions and continue frying until the onions are translucent. Season the mixture with salt, pepper and cumin, set aside and let cool.
Preheat the oven to 200 ° C.
Press the yeast dough into a greased springform pan and pull up an approx. 3-4 cm high rim (it is best to roll it out beforehand with a rolling pin) and let it rise for another 10 minutes.
Whisk egg, egg yolk, crème fraîche and cream and stir into the cooled onion mixture, distribute the mixture on the dough and bake the onion cake for about 30 - 35 minutes.