Crumble the yeast and mix with sugar until the yeast becomes liquid. (This saves the pre-dough.) Put flour, 1/4 teaspoon salt, oil and 175 ml lukewarm water into a bowl. Add mixed yeast and knead immediately to a smooth dough. Cover the dough and let it rise in a warm place for about 30 minutes
Season sour cream with a little salt and pepper. Drain tomatoes and olives in a sieve. Drain tuna also in a sieve
Line baking tray with baking paper. Halve the dough. Put 1 half on a baking tray and roll out very thin oval. Spread half of the sour cream on the bottom, sprinkle half of the olives and tomatoes on top. Spread half of the fish on top. Bake in the preheated oven on the lower shelf (electric oven: 250 °C/ convection oven: 225 °C/ gas: level 5) for 10-12 minutes. In the meantime, process the remaining dough and topping in the same way
Remove and bake the 2nd tarte flambée in the same way. Meanwhile wash the basil, dab dry and remove the leaves. Garnish the tarte flambée with basil
Waiting time approx. 30 minutes