Season fish of your choice with salt and keep aside.
Transfer kashmiri chillies,grated coconut, cumin seeds,turmeric powder,coriander seeds,tamarind ball,garlic cloves in a grinder jar. Add water as required and grind into a fine paste.
Heat oil in a deep pan and saute chopped onions unil translucent.
Then add finely chopped tomatoes,slitted green chilly and saute until tomatoes are mushy.
Now add the ground coconut masala paste in the pan and add water as required and mix well.
Wash the fish once and transfer it into the gravy, when the gravy starts to bubble.
Gently stir the fish in the gravy, not to break it. Let it cook on a medium heat.
When the gravy is slightly thick, add kokum at this point and also add salt if required after checking.
Once the gravy thickens as per your consistency then take it off the heat
Dish out and serve with steamed rice