Whisk together orange juice and next four ingredients. While whisking, add olive oil in a thin stream. Place fish in a glass or plastic container, top with jalapeno, onion and garlic and pour marinade over. Cover and refrigerate for 1 hour, turning once after 30 minutes. Remove fish and reserve marinade. Heat a large skillet over medium heat, add fish and brown on one side. Flip fish over, add marinade, onions, peppers and garlic and cook for 3 - 4 minutes. Remove fish when done and whisk in butter until melted. Spoon sauce over fish.