Pat fish dry with paper towels. Season fish with 1/4 tsp. salt and 1/4 tsp. pepper. Cook fish in hot oil in a large skillet over medium-high heat 3 to 4 minutes on each side or until fish flakes with a fork and is opaque throughout. Transfer fish to a serving platter, and keep warm.
Add onion and garlic to skillet, and sauté 1 to 2 minutes or until onion is tender. Stir in capers, basil, oregano, and remaining 1/4 tsp. salt; cook 1 minute. Reduce heat to low, add tomatoes, and cook, stirring occasionally, 10 minutes. Top fish with tomato sauce.
*Frozen halibut or fresh or frozen cod may be substituted.