In small bowl, combine parsley, lemon peel, oil and garlic; mix well. Set aside.
Line broiler pan with foil; spray foil with nonstick cooking spray. Place tuna steaks on foil-lined pan; sprinkle with salt.
Broil about 4 inches from heat for 4 to 5 minutes on each side or until fish flakes easily with fork, topping fish with parsley mixture during last minute of broiling time.