Clean and wash the fish. Add 1 tsp ginger garlic paste, ½ tsp turmeric powder and ½ tsp salt to the fish and mix well. Leave this for 15 minutes.
To a flat bottom vessel add 1 Tbsp of cooking oil and shallow fry the marinated fish on both sides for 5 minutes till they are cooked.
Remove the fish and add 3 Tbsp oil to the remaining oil in the vessel. This gives the fish flavor to the next steps.
Add fenugreek seeds, mustard seeds and cumin seeds to the oil.
Once they crackle add ginger garlic paste and mix for 30 seconds. Add chopped tomatoes, red chilli powder, turmeric powder, coriander powder and salt.
Fry all these ingredients till tomatoes are cooked and oil separates from the gravy.
Add fish pieces to the gravy and cook for 2 minutes. Add ½ cup of water (more water can be added as per choice of thickness for gravy). Cook for 7-8 minutes covering the vessel with a lid on low flame.
Add lemon juice and mix carefully.
Add coriander leaves to garnish.