Clean, wash and chop the beans. Cook in boiling salted water for about 10 minutes. Peel onions and cut into small strips. Wash and halve the tomatoes. Mix vinegar, salt, pepper and sugar. Fold in the oil.
Drain the beans. Put beans, tomatoes and onions in a bowl. Pour vinaigrette over them. Let lettuce steep for at least 30 minutes. Wash the basil, pluck the leaves from the stalks except for a little garnish, cut them coarsely and fold into the salad. Season again and garnish with basil
Waiting time approx. 30 minutes