These barbecued tuna steaks are a delicious and healthy option for a summer cookout. The tuna is marinated in a flavorful mixture of soy sauce, ginger, and garlic, then grilled to perfection. The walnut sauce adds a creamy and nutty element to the dish, complementing the smoky flavor of the tuna. Serve the tuna steaks with the walnut sauce drizzled on top, along with a side of grilled vegetables or a fresh salad.