4 eight-ounce halibut steaks, each sliced about 1 inch thick and cut lengthwise in half, or substitute any other firm white fish steaks of similar size
1. Wash the fish under cold running water and pat the pieces completely dry with paper towels. Sprinkle both sides of each piece with the lemon juice, 1 teaspoon of the salt, and the black pepper. Then set the fish aside on a platter to marinate at room temperature for 10 or 15 minutes.
2. In a heavy 10-to 12-inch skillet, heat the vegetable oil over moderate heat until a light haze forms above it. Drop in the onions and, stirring constantly, fry for 7 or 8 minutes, until they are soft and golden brown. Watch carefully for any sign of burning and regulate the heat accordingly.
3. Stir in the remaining ½ teaspoon of salt, the red pepper, turmeric and ground coriander. Fry for 30 seconds, then stir in the tomatoes and 2 tablespoons of the fresh coriander, and transfer the entire mixture to a bowl. Pour the remaining tablespoon of oil into the skillet, tipping the pan back and forth to spread it evenly over the surface of the pan.
4. Place the fish in the skillet and spread the tomato mixture evenly over the top of each piece of fish. Sprinkle with garam masala,cover tightly, and cook over low heat for 8 to 10 minutes, until the fish is firm to the touch and flakes easily when prodded gently with a fork.
5. To serve, transfer the fish to a heated platter, pour its sauce over it and sprinkle the top with the remaining 2 tablespoons of fresh coriander.
