In a mixing bowl or stand mixer, combine all-purpose flour, lukewarm water, and fine sea salt until a shaggy dough forms, about 2-3 minutes.

Drizzle in olive oil and knead for an additional 5 minutes until the dough is smooth and elastic.

Cover the dough with a damp towel and let it rest for 20 minutes to relax.

While the dough rests, heat a skillet over medium heat. Add chopped pancetta and cook until crispy, about 5-7 minutes.

Transfer to a paper towel-lined plate to drain. In the same skillet, sauté thinly sliced onions until they are tender and lightly caramelized, approximately 8-10 minutes.

In a separate bowl, mix crème fraîche with a pinch of sea salt, freshly ground black pepper, and a hint of nutmeg for added flavor.

Lightly flour your work surface and transfer the rested dough onto it.

Using a rolling pin, shape the dough into a rectangle approximately 9" x 18" in size.

Preheat your oven to 500°F.

Spread the seasoned crème fraîche evenly over the rolled-out dough, leaving a small border around the edges.

Sprinkle shredded Gruyere cheese generously on top, followed by the sautéed onions and crispy pancetta.

Carefully transfer the assembled Flammkuchen onto a baking sheet lined with parchment paper.

Bake in the preheated oven for about 12-15 minutes, or until the crust is golden-brown and the cheese is melted and bubbly.