Cut the tomatoes into coarse wedges, place them in a bowl with a generous pinch of salt and let them stand for fifteen minutes. They will release their juices, and it is precisely this tomato juice that will form the base of the dressing.
Tear the rye bread into coarse pieces and toast them in a frying pan with a tablespoon of olive oil until crispy on all sides. Rub the warm pieces with the halved garlic clove.
Slice the red onion into paper-thin half rings and rinse them briefly under cold water to take off the sharp edge.
Mix the collected tomato juice with the rest of the olive oil and the red wine vinegar to make a dressing. Toss the tomatoes, onion, olives and toasted bread through it and let it stand for ten minutes so the bread absorbs the liquid without becoming completely soggy. Tear the mozzarella into coarse pieces over it, finish with plenty of basil and black pepper. One slice of rye bread keeps the carbohydrates low while the mozzarella and olive oil provide protein and fat.