Apply salt, turmeric powder and red chili powder to the fish pieces and keep aside for 15 minutes.
Lightly roast cumin and coriander seeds. Mix with dry red chillies, soaked rice and grated coconut.
Grind it to a smooth paste. Soak tamarind in half a cup of hot water. Heat oil in a pan.
Add chopped onions and chopped ginger. Cook on a high flame till onions are golden brown. Stir in fish pieces and add 2 cups of water.
Bring it to a boil. Stir in coconut and spice paste. Mash tamarind dissolved in water to make a pulp.
Strain and add to the gravy. Simmer for 2 minutes and finish with coconut milk.
Add fish pieces and cook on a medium flame for 7-8 minutes or till the fish is done.