For the yeast dough, put flour, yeast, a pinch of salt and sugar in a bowl. Make a well in the middle and pour the cold water into it. Add the softened butter and knead into a smooth dough. This should then rest for at least 30 minutes.
For the topping, cut the onions into rings and fry them with the bacon in the oil. Whisk the eggs separately with the cream and season with salt, nutmeg and pepper. Mix both, season to taste and, if necessary, season again.
Finally, roll out the yeast dough, place it on a baking sheet and press the edges upwards. Place the topping on the dough, sprinkle with cheese and (if you like) caraway seeds and bake in a preheated oven at 200 ° C for about 30 minutes.
It is best to serve the finished onion cake warm.
A crunchy salad and a Federweißer (new wine) or a well-chilled white wine go well with it.