To make the dough, combine flour and salt.
Add remaining ingredients and knead until the dough is firm and elastic, about 10 minutes.
Cover and let the dough rest for 30 minutes, or refrigerate until ready to use.
To make the crème fraîche, place all ingredients in a bowl and stir until combined.
To make the flammkuchen, place a baking sheet in the oven and preheat the oven to 250°C (480°F).
Divide the dough into four equally sized pieces and place each piece on a sheet of parchment paper.
Roll out as thin as possible. Let the dough rest and relax for a minute or two from time to time, so that rolling is easier.
Thinly spread with crème fraîche and top with vegetables.
Carefully remove the hot baking sheet from the oven and slide the sheet of parchment paper with the flammkuchen on the baking sheet.
Bake for about 8-10 minutes or until the edges are crispy.
Repeat with the other three pieces of dough and serve immediately.