- In a large bowl with a wooden spoon or in a stand mixer fitted with the dough hook, combine the flour, yeast and salt. Add the water and beer. Mix until the dough forms a soft ball. On a lightly floured work surface or in the stand mixer, knead the dough for 5 minutes or until smooth.
- Form the dough into a ball and place in a clean, lightly oiled bowl, turning to coat with the oil. Cover with a damp cloth and let rise in a warm, humid spot for 2 hours or until doubled in volume.
- Meanwhile, in a large skillet over medium-low heat, soften the onions in the oil until translucent. Set aside in a bowl.
- Place a pizza stone or inverted baking sheet on the middle rack of the oven. Preheat the oven to 500°F (260°C).
- Divide the dough into 2 equal parts. On a lightly floured work surface, roll out one piece of dough to form a 15 x 10-inch (38 x 25 cm) oval. Place on a sheet of parchment paper. Repeat with the second piece of dough. Cover with an inverted baking sheet or plastic wrap and let rest for 15 minutes.
- Spread the crème fraîche over the dough. Generously season with pepper. Top with the onions, bacon and cheese.
- Place 1 flammekueche at a time (with the parchment paper) on the pizza stone. Cook for 8 to 10 minutes or until the dough is cooked and golden and the toppings are beginning to caramelize.