Heat broiler and spray broiler pan rack with nonstick cooking spray
Rub steak with cajun seasoning and place on prepared rack
Spread steak fries and onion around steak
Coat onion with cooking spray
Broil 7 minutes, remove onion, turn steak and fries over and broil 5 minutes longer or until steak is lightly charred (it will be medium-rare) and fries are crisp
Slice steak, drizzle with 1 Tbs. steak sauce and top with onion