Sprinkle fish with lemon juice and leave for 10 minutes. Wash in cold water and pat dry. Rub the fish with turmeric and salt.
Put the chili, tomatoes and ginger in a food processor and chop until smooth.
Heat the oil in a heavy based frying pan over low heat and fry the fish a few pieces at the time until brown on both sides.
Fry the panch phoron for 1 minute until aromatic. Add the tomatoes and fry for another 2 minutes. Add 200 ml of water and bring slowly to boil. Simmer for 3 minutes, add the fish, slowly return to boil and than simmer for another 3 minutes.
Sprinkle with the garam masala and salt to season. Serve with cooked jasmine rice.