Peel and finely dice the onion and garlic. Fry in hot oil. Chop the tomatoes in the tin and pour on. Simmer in an open pot for about 10 minutes while stirring. Puree with the cutting stick of the hand mixer. Season with salt, pepper and sugar.
Let the soup cool down. Wash the cucumber thoroughly and rub dry. Cut into cubes. Pluck basil leaves from the stalks. Add cucumber and basil to the soup. Sprinkle with parmesan