Wash the fish and marinate the fish with 1/2 tsp.of salt and a pinch of turmeric powder. Keep aside for 10 minutes. Heat oil in a frying pan. When hot, reduce the heat and fry the fish pieces till golden brown on both sides. Remove from oil,keep aside.

Add cumin seeds in the remaining oil. When the cumin becomes brown, add tomato.Saute for 3 to 4 minutes. Add ginger paste,saute for 2 minutes. Add cumin- chilli-turmeric powders, a pinch of sugar and 1/4 cup of water. Saute on slow flame until the raw smell of the masalas goes off. If needed add little water and saute for another few minutes. Add 1 to 11/2 cups of water and salt, let it bring to boil. Add the fried fish and cook for 7-8 minutes. Remove pan from heat, cover and give 10  minutes.

Tomato Rui is ready to serve.