Wash the tomatoes, dab them dry and cut them in half, cutting out the stalks. Peel and finely chop the onion. Pluck basil leaves from the stalks. Drain mozzarella and cut into slices. Cut olives into strips. Heat oil in a pan. Fry the tomato halves and onion for a few minutes.
Take them out. Fry basil leaves in the frying fat until crispy. Add vinegar, capers and olive slices. Season to taste with salt, pepper and sugar. Drizzle the vinaigrette over the tomatoes and arrange on plates. Ciabatta tastes good with it