Sift flour with salt. Heat the water to 55-60 ° C, mix with olive oil and pour into the flour. Knead a smooth, plastic dough. Roll into a ball and leave for 15-30 minutes.
Preheat the oven to 220°C by placing the baking sheet in the middle of the oven (the baking sheet must be hot). If you have a stone, warm it up.
Cut the onion into thin half rings and fry in olive oil until soft, cool slightly.
Cut the brisket into cubes.
Mix sour cream with salt, pepper, lemon juice and zest to taste.
Cut the baking paper to the size of the baking sheet and roll out the dough on it into a thin rectangular layer. Lubricate the dough with sour cream, sprinkle with onion and brisket, sprinkle with black pepper.
Bake Flamkuchen on a hot baking sheet for 10-15 minutes, until the pastry is golden brown. Serve hot.