Cut and clean fish into equal pieces of desired size.
Put red onion and red chili in a mixer and make a fine paste. Add red chili powder, turmeric powder and salt to the paste. Add fish pieces to this mixture and mix well so that the paste is all over the fish pieces. Marinate for 1 hour.
Heat oil in a deep fryer. Deep fry fish one by one when oil is hot. Serve with steamed rice.