Wash and marinate the fish pieces with turmeric powder, salt and lemon juice. Shallow fry the marinated fish.
Take a small bowl add turmeric powder, cumin powder, coriander powder kashmiri mirch powder, tomato paste and salt. Mix all spices with 2 tbsp water.
Take another small bowl make mustard paste with 1 tbsp mustard oil and little water and keep aside. In the same pan pour mustard oil and onion seeds. Just sauted and pour the mixed spices. Add slitted green chillies and stir for a minute.
Add the mustard paste again stir for a few seconds. Pour 1/2 glass of water let boil for a minute. Then add the fried fish and cook for a minute. Keep your palm above the curry if your palm is sticky then it is done.
See the consistency of the gravy and the gorgeous colour and flavour. Now it can be served with steamed rice.