1 Halve and squeeze orange. Mix orange juice with prawns and cayenne pepper.
2 Mix tomatoes with coconut milk and broth in a pot. Bring to a boil and cook for 5 minutes over low heat.
3 Meanwhile, trim scallions, rinse and cut diagonally into very thin rings.
4 Add prawns and orange juice to the soup and heat until prawns are cooked through. Season soup with salt and a little cayenne pepper to taste.
5 Ladle soup into soup plates or soup bowls. Sprinkle with scallions and serve.