Prepare the grill for two-zone cooking. Place lit coals on one half of the grill. If using a gas grill turn on only half of the burners. Make sure to brush the grates clean.
Mix the rub ingredients together in a medium bowl.
Butterfly the chicken breasts and then coat the chicken evenly in the rub. Let the chicken sit at room temperature for 20 minutes to let the rub set.
Once the grill is preheated and the rub is set, place the chicken directly over the heat and grill until done. Roughly 7-8 minutes per side. You may need to turn them once or twice during cooking to get them to cook uniformly.
During the last 4-5 minutes of cooking wrap the tortillas in foil and place them on the indirect side of the grill. Flip them half-way through.
When the chicken is fully cooked and the juices run clear, remove from the grill and place on a cutting board. Remove the tortillas from the grill too. Don't want them to burn.
Slice the chicken and serve over the warm tortillas. Serve with your favorite salsa, sour cream, guacamole and cheese.