Preheat the Oven. Preheat your oven to 475°F and place a baking stone or sheet pan inside to heat up.
Prepare the Dough. Roll out the pizza dough thinly on a piece of parchment paper.
Assemble the Tart. Spread a layer of crème fraîche evenly over the dough, leaving a small border around the edges. Top with crispy bacon and thinly sliced onions. Season with salt and pepper.
Bake to Perfection. Carefully transfer the tart, still on the parchment paper, onto the preheated baking stone or sheet pan in the oven. Bake for 10-12 minutes or until the edges are golden brown and crispy.
Serve and Enjoy. Remove from the oven, sprinkle generously with Gruyère cheese, and serve hot. Slice into squares or wedges and enjoy!