Peel and wash the potatoes and slice them into thin slices. Peel onions, cut into rings. Wash thyme, dab dry, pluck leaves from the stems
Heat the oil in a frying pan. Fry the onions for 2-3 minutes. Add sugar, caramelise, deglaze with vinegar and bring to the boil. Stir in thyme. Season with salt and pepper, put into a sieve, drain, collect the stock
Mix sour cream and crème fraîche, season with salt and pepper. Take the tarte flambée dough out of the package and unroll it with the baking paper directly on a baking tray. spread the dough with cream, cover with potatoes and onions
Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 15 minutes. Remove the tarte flambée, cut into pieces and sprinkle with stock if necessary