Marinate the fish pieces with salt and turmeric powder, and set them aside for 10 minutes.
Heat oil in a pan.
Add the fish pieces one by one to the hot oil.
Fry them until they turn golden brown.
Remove the fried fish pieces from the pan.
Add whole cumin seeds, then add chopped tomatoes and onion-ginger-garlic paste in the remaining hot oil. Give them a good stir.
Add all the powdered spices (termeric, red chili, kashmiri red chili, coriander, and cumin) and a little bit of salt.
Stir for a few minutes. Add a small amount of water and mix well.
The add 1 cup of water for the gravy (you can increase or decrease water for your required gravy consistency).
Once the water comes to a boil, add the fried fish gently to the cooking pan.
Cover the pan with a lid.
Add roasted cumin powder and 2-3 green chilis.
Let the gravy simmer for a few more minutes. Sprinkle coriander leaves and turn off the gas.
Fish masala is ready to be transferred to a bowl. Serve it along with steamed basmati rice or Naan, roti or chapati.