Add some salt and turmeric power to the cleaned fish and keep aside.
Extract pulp from the soaked tamarind.
To the Tamarind pulp add tomatoes and crush well.
To this add crushed onion, green chilies, crushed ginger, curry leaves, coriander leaves, chili power, coriander powder, turmeric powder, enough water and salt to taste. Keep aside.
Heat oil in a vessel or an earthen pot.
Add the curry vadam. Once they splutter add the prepared mixture and cook covered for 5 minutes.
Cook covered till the curry reduces a bit.
Add the fish pieces and cook covered till they are well cooked.
Pour one tbsp gingeley oil, crushed garlic, crushed pepper and the roughly chopped coriander leaves and cook for a minute. Remove from fire.
Heat the remaining gingeley oil in a small kadai.
Add the finely chopped onion and fry till they are browned and nice aroma arises.
Pour this on to the curry and keep it closed. Serve hot with rice, idli or dosa.
Happy cooking :)