Preheat the oven to 240°C. Sauté the bacon bits in a very hot skillet for about 2 minutes over high heat until they are lightly browned.
Peel the onion, cut it in half, and then slice it thinly into strips.
Mix equal parts crème fraîche and fromage blanc in a mixing bowl. Season with salt, pepper, and a pinch of ground nutmeg, then stir until the mixture is smooth.
Roll out the dough on a baking sheet. Fold the edges in slightly, if desired, to form a flammekueche with clean, defined edges.
Spread the cream mixture evenly over the entire surface of the pastry, leaving about 1 to 2 cm free around the edges.
Add the thinly sliced onions and bacon bits evenly. Then bake for 10 to 15 minutes, until the crust is golden brown and crispy.
