1. Whisk together first 3 ingredients in a large bowl until smooth; whisk in buttermilk, next 3 ingredients, and 2 tsp. salt until blended.
2. Place buttermilk mixture and chicken in a large zip-top plastic freezer bag; seal and chill 3 hours.
3. Meanwhile, soak wooden skewers in water 30 minutes. (Omit if using metal skewers.)
4. Coat cold cooking grate of grill with cooking spray, and place on grill. Preheat grill to 350° to 400° (medium-high) heat. Remove chicken from marinade, discarding marinade. Thread chicken onto skewers, leaving a 1/8-inch space between pieces; sprinkle with remaining 1/4 tsp. salt.
5. Grill kabobs, covered with grill lid, 6 to 8 minutes on each side or until chicken is done. Serve with lemon halves and Toasted Pecan Pesto or Romesco Sauce.