Sprinkle chicken with blackening seasoning and place on grill when hot. Cook 6-7 minutes per side, or until cooked through.
While chicken is cooking, add lettuce, parmesan, and tomatoes to a large salad bowl.
When chicken is cooked, let rest for at least 5 minutes. Slice and then lay over the lettuce. Sprinkle with fried onions and then drizzle with dressing. Season with pepper.