Place tuna in single layer in large shallow glass dish. Combine sherry, soy sauce, sesame oil, hot chili oil and garlic in small bowl. Reserve 1/4 cup soy sauce mixture at room temperature. Pour remaining soy sauce mixture over tuna. Cover; marinate in refrigerator 40 minutes, turning once.

Spray grid with nonstick cooking spray. Prepare grill for direct grilling.

Drain tuna, discarding marinade. Place tuna on grid. Grill, uncovered, over medium-hot coals 6 minutes or until tuna is opaque, but still feels somewhat soft in center,* turning halfway through grilling time. Transfer tuna to carving board. Cut each tuna steak into thin slices; fan out slices onto serving plates. Drizzle tuna slices with reserved soy sauce mixture; sprinkle with cilantro.