DO-AHEAD TIP: Marinate chicken for 30 minutes (see recipe).
Preheat grill to MEDIUM. Place chicken in a large zipper-topped plastic bag. In a small bowl, combine next 7 ingredients (garlic through black pepper).
Pour mixture over chicken, seal bag and gently rub mixture into chicken to coat well. Refrigerate for 30 minutes. Lightly oil the grill grate and cook chicken over indirect heat for 6 to 8 minutes per side or until juices run clear.
Watch carefully to prevent burning! Top each chicken breast half with a slice of tomato followed by a slice of cheese and serve when melted. Enjoy!