In a sauce pan mix together onion, tomatoes, ginger, garlic, coconut milk, coriander, chilli and pepper powder, add water to obtain the desired consistency
Place sauce pan on medium heat and let the mixture cook, stir occasionally, once the gravy starts boiling turn heat to low and continue cooking until gravy slightly changes color, check for seasoning add fish and let it continue cooking until fish is cooked, stir in tamarind paste if using, turn heat off and let it rest for 10 before serving.
If not using tamarind paste, you could use juice of a lime, stir in just before serving.
