1. Wash and clean the silver pomfret and cut in large pieces.
2. Sprinkle 1/2 teaspoon salt over this, rub the salt well in the pomfret and keep aside.
3. Place a deep flat pan on medium heat and add 5 tablespoons oil. add 1 medium onion finely chopped and fry for a minute.
4. Add 5 to 6 garlic cloves finely chopped, 5 to 6 green chillies finely chopped and fry for another 2 minutes.
5. Add 1.5 tablespoons all purpose flour and fry for 1 minute. add 1 cup water and mix everything, it will turn into a slightly thick sauce.
6. Add additional 1/2 cup water to thin this sauce and stir. also add 1 teaspoon salt and stir it in.
7. Add 2 tablespoons dark vinegar and stir it in. also add 1/2 teaspoon cumin powder, 3 teaspoons sugar and stir everything together.
8. Add the silver pomfret, keep aside and stir gently.
9. Cover the silver pomfret with the sauce and add 1 medium tomato chopped over the pomfret and at the sides. cover and cook for 3 minutes.
10. Open the pan, pick it up and gently swirl the pan so the sauce and tomatoes mix well. gently cover a bit of sauce on the top of the fish.
11. Add 2 tablespoons chopped fresh coriander leaves. cover and cook for another 3 minutes.
12. Open and simmer for a minute and remove from heat. enjoy this lovely fish with some hot basmati rice or parsi khichidi.