Take the Ahi Tuna out of the refrigerator. Remove the packaging, and set aside.
In a large dish, mix all of the marinade ingredients together. Reserve about four tablespoons of the marinade. Add the tuna steaks to the dish, and turn them until they’re well-coated. Set aside, and let them rest at room temperature for about 20-30 minutes.
Heat up a non-stick skillet over high heat. Sear the tuna steaks for about 1-3 minutes on each side, or until the steaks reach their desired doneness.*
Place the cooked steaks on a cutting board, and slice against the grain into ½-inch thick slices. Transfer the steak slices to a serving plate and drizzle with the reserved maple-mustard marinade. Serve immediately.