Place the basil leaves, olive oil, vinegar, soy sauce, pepper, sugar, salt and 2 tablespoons hot water in a blender and puree. Arrange the tuna steaks in a baking dish large enough to hold them in a single layer. Pour the marinade over the fish. Cover and marinate for 3-4 hours in the refrigerator - turning the steaks occasionally. Prepare coals for grilling or preheat the broiler. Drain the tuna steaks and grill them over medium-hot coals or broil 4-5 inches from the heat until charred on the outside but still pink in the center - about 3 minutes - turning the steaks once. Do not overcook. Remove from the heat and place the steaks on warmed dinner plates. Melt 2 tablespoons butter in a large skillet over medium-high heat. Add to the skillet the banana, pineapple, mango, papaya, fresh cilantro leaves, lemon juice and sugar. Stir. Cook on low until mixture starts to get warm. Add the brown sugar and rum. Stir and heat thru. Taste sauce and adjust with lemon juice, brown sugar and rum to desired taste. Do not overcook. Spoon the sauteed fruit mixture over the tuna and serve immediately. NOTES : .....Borrowing the Southwestern idea of serving fruit salsa with grilled food, I pair grilled tuna steaks with an unusually fresh-tasting strawberry salsa, which looks as colorful as it is luscious. Recipe by: Adapted from Fruit Cookbook by Nicole Routhiers Posted to EAT-L Digest by Sharon on Feb 7, 1998