Mix the flour, yeast, salt, oil and water into a smooth yeast dough (you don`t even need to dissolve the yeast in the food processor beforehand), let the dough rise for approx. 45 minutes.
Preheat the oven to 200 °.
In the meantime, peel the onions, quarter them and cut across into slices, sauté in the butter until translucent. Whisk the créme fraîche and eggs, add to the onions.
Roll out the dough and place in a greased tart pan, cutting the dough 1 - 2 cm above the edge. (works best with standard scissors). Spread the topping on the yeast base and sprinkle the bacon on top. Fold the protruding edge inwards and bake in the preheated oven at 200 ° for approx. 50 minutes.
The protruding edge, later folded inwards, prevents the filling from leaking out.