1- Wash the fish well in salt water. Apply the lemon juice to the fish and set aside for approximately 1 hour.
2- Fry the onions till they are light golden in color. Remove with a slotted spoon and crush. In the same oil put the red chillies, onion seeds, turmeric powder, red chilly powder and garlic. Stir and fry for a few minutes till the oil separates.
3- Add the yogurt and again stir and cook till the oil separates. Add the fish. Coarsely grind together the white cumin seeds, aniseed, coriander seeds, fenugreek seeds and mustard seeds.
4- Add this to the fish along with the green chillies and cook over a low heat till the fish is done, about 10 min.