Peel, wash and cut the kohlrabi into fine sticks. Wash, clean and quarter the tomatoes. Remove seeds and cut the flesh into small cubes. Mix stock and tomato paste and bring to the boil in a pot.
Add kohlrabi pencils and cook for 5-8 minutes. Add tomato cubes shortly before the end of cooking time and heat up as well. Season soup with salt and pepper if necessary. Cut cress from the stems, wash and sprinkle over the soup before serving