Add all marinade ingredients to a large mixing bowl, stir to combine. Slice chicken into 1” pieces and add to marinade. Toss everything to coat, cover with plastic wrap and refrigerate 3-6 hours.
When ready to cook, thread pieces of chicken onto metal skewers and alternate with slices of red onion and whole cherry tomatoes. Note: if using bamboo skewers, soak skewers in water 1 hour ahead of time.
Preheat grill or grill pan to med heat. Cook kebabs over direct heat approximately 6-7 min per side or until meat reaches internal temperature of 160F.
Remove from grill and cover with foil for 5 minutes before serving.