For the salad, rinse and trim the lettuces, drain well and tear into bite-sized pieces. Rinse and trim the radishes and cucumber and slice both thinly. Peel the onion and cut into rings. Arrange everything in a bowl or on plates.
For the dressing, mix the vinegar with the oil and garlic and season with the spices. Stir in the finely chopped lemon balm.
Serve the salad drizzled with the dressing.