1. Combine flour, salt, lukewarm water, oil, and the egg yolk and knead to get a smooth dough. Brush the dough with a little additional olive oil and place it in a tight-sealing container. Let it rest at room temperature for about 30 minutes.

2. Preheat the oven to 230°C (450°F) fan-forced. Mix the sour cream with the crème fraîche and season well with salt and pepper. Peel the onions and cut them into thin rings. Wash, dry, and half the tomatoes. Wash and drain the arugula.

3. Divide the dough into four portions (or two portions for two large Flammkuchen). Place one portion of the dough on a piece of baking parchment and roll it out very thinly with a rolling pin. If the dough does not want to comply, you can simply stretch it over the back of your hands, like you would do with pizza dough – this is often the most effective method. Spread the cream all the way to the edges of the flat dough and distribute onion rings evenly on top. Pull the Flammkuchen with the baking parchment onto the baking sheets and bake them for about 10-12 minutes until nicely browned around the edges. When using a convection oven, you can easily bake to baking sheets at the same time.

4. Top the baked Flammkuchen with the halved tomatoes, arugula, and Serrano ham, and drizzle with balsamic vinegar cream to your liking.