In a bowl mix the yeast, flour and salt. Make a well in the center and pour the lukewarm water. Knead into a smooth dough. Cover the bowl with a damp a dish towel and let the dough rise for 1 hour.
Preheat the oven to 250ºC. Cut the bacon into strips as thin as possible. Roll out the dough with a rolling pin on a baking sheet lined with parchment paper to a thickness of 1 cm. Mix the sour cream with the soft curd and season with nutmeg, salt and pepper. Spread this mixture over the dough. Cut the onion into rings. Cover the dough evenly with the bacon and out. Sprinkle over the Cheese Crumbles. Bake the flammkuchen approx 65 min. In the middle of the oven.