Season the tomatoes with salt, pepper and herbs from Provence. Cut Cabanossi diagonally into slices. Wash the tomatoes and possibly halve them. Peel onions and cut them into fine rings.
Slice the flat bread horizontally. Spread halves thinly with tomato sauce. Cover with cabanossi, tomatoes and onion rings. Crumble the feta cheese and sprinkle it evenly on top. Put flat breads on 2 baking trays lined with baking paper.
Bake the trays one after the other in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 10 minutes until golden brown. In the meantime, wash the basil, dab dry and pluck the leaves from the stalks.
Take the flatbreads out of the oven. Cover with olives and basil and serve immediately.