Sauce: In a large bowl mix together: tomato, onion, cilantro, Chiles Serranos, olive oil and lime juice. Cover and refrigerate for approximately one hour for the flavors to marry. Remove from the refrigerator, and let it warm at room temperature.
Fish: rub olive oil on the fish and season with salt and black pepper. Cook the fish fillets on a grill or in a broiler until tender (be mindful not to overcook).