Onions peel, halve and in fine strips cut. Wash and clean the tomatoes and cut them into slices or halve them. Wash parsley, shake dry, pluck leaves from the stalks.
Mix vinegar, salt, pepper and sugar well. Add the oil. Mix vinaigrette with tomatoes, onions and parsley. Leave to stand for about 30 minutes. Cut the pomegranate in half and knock the seeds out of their skin using the back of a spoon.
Arrange the tomato salad in a bowl and spread pomegranate seeds over it.