Prepare the pizza dough: Place the water, salt, sugar, flour, and yeast in the bowl of a stand mixer fitted with the dough hook. Knead for five minutes on speed 1, followed by five to six minutes on speed 2. Two minutes before the end of the kneading time, drizzle in the olive oil with the mixer running.
Continue kneading until smooth. Shape the dough into a ball and place it in a lightly oiled bowl. Cover the bowl and let the dough rise for two hours. Fold the dough once, after an hour.
Preheat the oven to 450° F (240° C/Gas Mark 8). Turn the dough out onto a floured work surface, shape it into a ball, and let it rest for 20 minutes.
Meanwhile, peel the onions and slice them very thinly. Cut the bacon into thin strips. If your onion and bacon slices are a little thick you can sauté them together in a skillet for five minutes to soften and cook them a bit before adding them to the flammenküche. Let cool completely on a plate lined
with paper towel to absorb excess grease before using.
In a bowl, stir together the fromage blanc and crème fraîchee until smooth. Season to taste with salt, pepper and nutmeg.
Place the dough on a baking sheet, either non-stick or lined with parchment paper. Using your fingertips or a rolling pin, press or roll the dough out into as thin a circle as possible.
Spread the cheese mixture over the dough in an even Iayer, then scatter the onions and bacon over the cheese.
Bake the flammenküche for 10 minutes, without letting it brown. Serve warm or at room temperature.