Clean, wash and cut Bombay duck into one and a half inch sized pieces. Soak tamarind in a little warm water for the pulp.
Lightly roast black peppercorns. Apply turmeric powder, salt, lemon juice, ginger paste, garlic paste, green chilli paste to the fish pieces.
Keep it aside for fifteen to twenty minutes to marinate well. Grind onion, coconut, roasted peppercorns and tamarind with a little water to a fine paste.
Heat oil in a vessel, add the ground paste, sauté on low heat till it starts giving flavour.
Add one cup of water and let the gravy cook for ten to fifteen minutes or till it becomes thick.
Add marinated Bombay duck pieces and simmer it for four to five minutes. Check the seasoning.
Serve hot garnished with coriander leaves.