Cut fish into strips 2 inches wide. Rub on all sides with mixture of red pepper, turmeric, 1 teaspoon salt, and lemon juice. In a nonstick frying pan heat 1 tablespoon oil over medium heat and lightly brown the fish in 2 batches if necessary, placing skin side down and turning after 1 or 2 minutes. Remove fish from pan and set aside.
In the same pan wiped clean, over medium heat, fry onion in 2 tablespoons oil until light brown. Add garlic and mustard seeds and stir for 1 minute. Add tomatoes and spice mixture and fry until tomatoes become very soft and break up. Add cilantro and salt and continue stirring until the mixture becomes a paste.
Remove from heat, add yogurt, and stir to blend.
Arrange fish in a single layer in a baking dish. Pour sauce over fish, cover with aluminum foil, and bake in preheated oven for 20 minutes until opaque.
Recipe courtesy of Maya Kaimal MacMillan, author, Curried Flavors