Peel and dice the onions. Clean the celery and zucchini and cut into pieces.
Heat the oil, sauté the onions (garlic) until translucent, add the celery and zucchini and sauté for about 4 minutes. Pour in tomatoes and broth, add sugar and simmer covered for approx. 20 minutes.
Puree the soup, add the cream or sour cream, season with salt, pepper and basil or garnish.