Cut the radish greens into small pieces, rinse, dry well and chop in a universal chopper, set aside 1 tbsp. for garnish. Sauté the rest of the greens in the melted light butter or possibly butter on 3 or possibly automatic heat 11-12.
Add lemon zest, fill up with clear soup. Stir sour cream or crème fraiche and flour, add to the boiling soup and cook for 5 minutes on 1 or possibly on automatic heat 5-6.
In the meantime, rinse radish, remove peel and grate coarsely with shredder. Simmer the radish in the soup for 2 minutes. Season the soup with salt and freshly ground pepper and serve with the remaining radish greens.