Marinate the fish with the marinade ingredients.
Heat 1 Tbsp of oil in a pan. Add in all the seasoning ingredients and let them splutter.
Add in the onions and fry them until brown.
Add the green chillies, turmeric and ginger garlic paste.
Add the tamarind water, salt and the chilli powder and let it boil.
In the meantime, in a separate pan, fry the ingredients of the Ground paste in a few drops of oil - except the cumin seeds, curry leaves and garlic. Let them cool. Then grind all Ground paste ingredients with a drop of water and make a smooth paste.
When the tamarind water is boiled add the marinated fish and let it cook slowly for about 10-15 minutes or until it's cooked.
When the fish is cooked, mix in the Ground paste.
Garnish with coriander leaves and serve hot with rice.