For the dough crumble yeast and dissolve with sugar in 175 ml lukewarm water. Knead with flour, 1⁄2 TL salt and oil to a smooth dough. Cover and leave to rise in a warm place for about 45 minutes.
In the meantime, clean and wash the spring onions and cut them into rings for the topping. Quarter bacon slices. Wash thyme, shake dry and pluck off the leaves. Mix sour cream with thyme, salt and pepper.
Express sauerkraut.
Knead the dough again and cut in half. Roll out each half on baking paper oval (25 x 35 cm) 2-3 mm thick. Spread with sour cream. Spread sauerkraut, spring onions and bacon evenly on top.
Bake one after the other in the preheated oven on the bottom rack (electric oven: 250 °C/circulating air: 225 °C/gas: see manufacturer) for 10-12 minutes. Serve the tarte flambée immediately.