Remove the skin from 2 tomatoes, remove the seeds and cut into cubes. Rinse the remaining tomatoes, remove the stalk and cut into quarters.
Put the tomato quarters in the cold vegetable soup. Add the tomato pulp and simmer at a low temperature for 20 minutes. Season everything with salt and pepper and a pinch of sugar.
For the ricotta dumplings, finely chop the basil. Add the stalks to the soup. Mix the ricotta with the egg yolks, flour and chopped basil and stir well. Make small dumplings from the mixture and boil them in salted water for 5 minutes.
Strain the soup through a fine kitchen towel and season again.
Put the diced tomatoes and dumplings in the soup plates and pour the soup over them.