Put flour and 1 pinch of salt in a bowl. Stir the yeast with 1 teaspoon sugar until liquid, add to the flour. Add approx. 175 ml lukewarm water and oil. Knead everything to a smooth dough, form into a ball. Cover and leave to rise in a warm place for about 1 hour.
Wash the apple and remove the core with an apple corer. Slice or cut the apple into thin slices. Sprinkle with lemon juice. Mix quark, sour cream and vanilla sugar. Mix 2 tbsp. sugar and 1 tsp. cinnamon.
Preheat oven (electric cooker: 220 °C/circulating air: 200 °C/gas: see manufacturer). Line baking tray with baking paper. Roll out the dough thinly. Spread with quark cream and cover with apple slices. Sprinkle with nut flakes and cinnamon sugar. Bake in a hot oven for 12-15 minutes, remove from oven. Sprinkle with caramel and sprinkle with lemon thyme as desired.
Express! For all those in a hurry, there is ready-made tarte flambée dough from the refrigerated shelf (e.g. from Aunt Fanny).