Blend together mayo, buttermilk and next five ingredients. Pour 1 cup of dressing into a large ziplock back. Add chicken breasts. Seal and chill at least 30 minutes or overnight.
Preheat oven to 375. Discard marinade and place chicken breasts side by side in a shallow baking dish. Bake 20-25 minutes until chicken is cooked through. Top with additional dressing and serve with rice if desired. Enjoy!
Extra sauce can be stored in airtight container in the fridge up to three days.