Marinate the fish in pepper powder, salt and vinegar and keep aside for 30 minutes.
Heat oil in a pan and temper with bay leaves, red chillies and garam masala. Add garlic and onion paste and saute on low heat for a few minutes.
Add melon and poppy seeds paste, sugar and salt and saute until the oil begins to separate. Toss in the fish, cover and cook on low heat for 8-10 minutes.
Uncover, fish the flip and add chillies. Cover and cook for 5 more minutes.
Once the gravy is reduced, add Kewra essence and serve garnished with green chillies and onion rings.