In a saucepan heat 2 tablespoons of the oil over high heat. Add onions and saute 1 minute. Stir in garlic, tomatoes, olives, anchovies, chopped basil, parsley and oregano; season with salt and 10 turns of pepper. Bring to a boil and simmer, stirring occasionally, about 3 minutes. Reduce heat to medium and add butter pieces, stirring. When butter is half melted, remove saucepan from heat and continue stirring until thoroughly incorporated.
In a saute pan heat oil over high heat. Season tuna steaks with salt, pepper and Creole seasoning and sear until well-browned, about 2 minutes per side, turning once. Pour tomato sauce mixture over tuna steaks and bring to a gentle simmer. Continue cooking until tuna is medium-rare, about 5 minutes more. To serve, transfer tuna to 2 heated plates, spoon some sauce over and around steaks and garnish with basil chiffonade.
Yield: 2 servings