Put the flour, 1 egg, salt, pepper and nutmeg in a bowl. Add the butter and knead everything with your hands. Let the dough cool in the refrigerator for 2 hours.
Roll out very thinly on a greased baking sheet or on parchment paper. Remove excess margins. Poke holes in the dough with a fork.
Steam sliced onions and optionally pork belly in a pan for 4 minutes.
Beat 2 eggs and season with salt, pepper and nutmeg. Add the onions, bacon, sour cream and herbs. Pour everything over the dough. If you like to have a cheese crust, you can now pour the grated cheese over it.