For the dough, knead the flour with the water and a pinch of salt and cover it for about 15 minutes.
For the topping, mix the crème fraîche with salt, pepper and nutmeg. Peel the onion and cut into rings, dice the ham and wash the chives, shake dry and cut into small pieces.
Preheat a pizza stone on the grill for about 30 minutes at at least 250 degrees.
Flour a cake board and roll out the dough thinly to a size of approx. 35 cm in diameter. The board should be floured again so that the tarte flambée can slide easily onto the pizza stone.
Spread the prepared crème fraîche evenly, then spread the diced ham and the onion on top. Let the tarte flambée slide onto the hot pizza stone and bake for about 8 minutes.