Heat oil in a large saucepan over medium heat. Add onion, capsicum, garlic and chilli, then cook for 5 minutes, stirring, or until very soft. Add the tomato paste, and cook, stirring, for 1 minute.
Add the chopped tomatoes, sugar, coconut milk, stock and spring onion, bring to a simmer, then add the seafood. Cover and simmer for 5 minutes or until the prawns and fish are cooked through and just opaque in centre.
Add lime juice and season. Transfer to a serving dish, garnish with coriander and serve with crusty bread for soaking up the sauce.
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