Drain the corn. Peel and finely chop the onion. Peel, wash and chop the sweet potato. Heat the oil in a large pot. Fry the onion until transparent. Add corn and sweet potato and steam for about 2 minutes.
Deglaze with 1 l water and tomatoes. Stir in the stock. Bring everything to the boil and simmer for about 15 minutes.
Wash the lime in hot water, dry and grate the peel. Squeeze the lime. Remove approx. 1⁄4 from the soup and set aside. Finely puree the rest of the soup with a hand blender. Stir in lime zest and juice, cream, tortelloni and the soup that has been set aside.
Warm everything up.
Wash the basil, shake dry, pluck the leaves and cut into strips. Season soup with salt and pepper and serve sprinkled with basil.