Clean and wash the fish; pat dry. Add turmeric power, salt and lime juice and set aside for 15 mins.
Add sliced onions, chilies, nigella/onion seeds, gram flour and salt to the fish and mix well. Let it rest for 15 more minutes.
After 15 minutes the onions and fish will have released just enough water to moisten the gram flour so the onions stick together. You want the batter to be of a doughy consistency, not too free-form. You may add slight water to moisten it just enough so they don't fall apart. Try to use as little water as possible.
Heat enough oil in a pan to deep fry the fritters (about 2 inches).
Drop the fritter batter into the hot oil by the tablespoonful, a few at a time, and fry over medium heat, turning once, until the fritters are golden brown on both sides, about 2 minutes on each side. The fritters will have an irregular shape with a few loose pieces of onion and fish escaping here and there. Check one fritter by breaking it open to see if the center Is cooked; it it still seems unset, cook 1 minute more. Drain on paper towels.
Serve with kashundi and hot tea.