1. Combine first 4 ingredients in a shallow dish or large plastic zip-top bag. Add chicken and onion, stirring to cover. Refrigerate 3 to 6 hours.
2. Drain chicken and onion; discard marinade. Thread chicken, onion, and next 3 ingredients on 10 or 12 (10-inch) skewers. Brush with Lime-Cayenne Butter.
3. Grill over medium heat (325° to 350°) for 8 to 10 minutes or until chicken is cooked through, turning and basting several times with Lime-Cayenne Butter.