Marinate the fish with salt to taste, pinch of turmeric powder and a pinch of red chilli powder for 10-15 minutes.
Heat 2 tbsp. oil and shallow fry them till light golden in colour. Keep aside.
Dry roast the coconut till light golden brown and keep aside.
Heat 1 tbsp. oil and.temper with the fennel seeds. Saute for a few seconds. Add the chopped garlic, followed by the onions. Fry till light brown in colour.
Add 1 chopped tomato and fry till well mashed up.
Add the turmeric powder, red chilli powder and roasted coriander powder and the dry roasted coconut. Mix well. When cool, grind into a paste with 2-3 tbsp. water. Keep aside.
Add the remaining oil and temper with mustard seeds, cumin seeds and fenugreek seeds. Saute till it stops crackling. Add the sambar onion and green chilies, Saute till light brown in colour.
Now add the ground paste and continue to saute till the oil separates.
Add the tamarind water, 1 cup plain water, curry leaves and salt. Let it come to a boil. Add the fried fish and tomatoes. Cover and simmer for 7-8 minutes on low flame....... till the gravy slightly thickens.
Serve, garnished with coriander leaves and green / red chilies.
