Rinse fish; pat dry. Drizzle 2 teaspoons of the oil over swordfish. Sprinkle with 1/4 teaspoon each of salt and black pepper. Grill on the lightly greased rack of an uncovered grill directly over medium heat for 8 to 12 minutes or until fish flakes easily when tested with a fork; turn once.
Meanwhile, for the spicy tomato sauce, in a medium skillet heat the remaining oil. Add onion, serrano or jalapeno pepper, garlic, turmeric, and coriander; cook about 2 minutes or until onions are tender. Stir in tomatoes and 1/4 teaspoon salt; cook 2 to 3 minutes or until tomatoes are just tender. Remove from heat; stir in cilantro. Serve spicy tomato sauce over fish. If desired, serve with couscous. Makes 4 servings.