Pick up the lettuce hearts, wash and cut into bite-sized pieces. Cut the tomatoes into wedges. Peel the onion and cut into small cubes.
Put the onion cubes in a salad bowl, pour the salt, pepper and salad herbs over it.
Mix a dressing from the remaining ingredients except for the basil leaves, pour over the onions and stir everything again well. Carefully fold in the lettuce hearts and tomatoes and finally sprinkle with the basil cut into strips.