Place the fish in a shallow dish. Combine the cilantro, oil, lime juice, and black pepper and pour over the fish. Cover the container and marinate the fish in the refrigerator for about 30 minutes (but no longer than 2 hours).
Meanwhile, combine tomatoes, onion and garlic in medium bowl; stir in the serrano peppers and mix well.
Spray a medium nonstick skillet with cooking spray and place over high heat. Once the skillet is hot, add the fish and cook for 4-5 minutes on each side (or until fish is lightly browned and no longer opaque).
Remove the fish and place it on a platter to keep warm; set aside.Reduce the skillet to medium heat and add the tomato mixture. Cook, stirring frequently, for about 3 minutes or just until onions are soft. Return the fish to the skillet and cook for an additional 2 minutes to heat through.
Divide the fish and tomato mixture between four serving plates and sprinkle the tops with the cilantro and any remaining lime juice alongside, or on top of a serving of rice.
