Place the prawns in a bowl with 2 tbsp of the lime juice, 1 tsp of salt and 1 tbsp of the chopped garlic. Chill for 1 hr.
Heat the coconut oil in a large saucepan. Add the spring onion and onion and fry for 5 mins, then add the red pepper, chilli flakes, paprika and remaining garlic.
Pour in the tomatoes, coconut milk and a little salt. Bring to a simmer and let reduce for 10 mins. Add the prawns, all the marinade and remaining lime juice. Gently simmer until the prawns turn white, about 3 mins. Serve with the fresh coriander and rice.