In large skillet over medium heat, sauté fennel and onion in 2 T olive oil for 5 minutes. Add garlic, lemon, salt and pepper and sauté for 2-3 minutes more. Transfer to a plate and set aside. In same skillet over medium-high heat, add more olive oil and cook halibut
on each side for 3-5 minutes. Add fennel mixture back into skillet, arranging around the fish. Then add olives, tomatoes and wine.
Cover and cook for 3-4 minutes. Remove lid and add butter. Cook for a few more minutes. Add salt and pepper to taste if needed. Plate the fish and serve drizzled with pan juices and fresh fennel fronds. Serves 3-4.