Peel and finely chop the onion. Heat 1 tablespoon of oil. Sauté the onion in it until translucent and briefly sauté the tomato paste. Add canned tomatoes and juice and chop a little. Stir in 1/4 l water and stock. Bring to the boil, cover and simmer for about 15 minutes.
Heat 2 tablespoons of oil in a frying pan. Cut the bread into cubes and toast them crisply in it. Salt and drain on kitchen paper
Wash the tomatoes and cut into slices. Puree the soup lightly and stir in the herbs. Season to taste with salt, pepper and sugar. Heat the tomato slices in the soup
Whip cream until semi-stiff and carefully fold into the soup. Sprinkle with the croutons before serving