In a medium mixing bowl whisk together the buttermilk, minced cilantro, lime zest and juice, minced garlic, chili powder, Frank's RedHot, smoked paprika, chipotle chile powder, and ground cumin until evenly combined.
Place the chicken drumettes into a 1-gallon zip-top bag and pour in the buttermilk marinade.
Seal the bag, press out excess air, and massage the bag so each piece is coated with the marinade.
Put the sealed bag zip-side up in a small casserole dish to catch any leaks and refrigerate for at least 4 hours or ideally overnight.
When ready to cook, preheat your grill to medium heat.
Remove the drumettes from the marinade and shake off excess; discard the marinade. Grill the drumettes over medium heat for about 8–12 minutes, turning occasionally, until the outside is crisp and the internal temperature reaches 165°F (74°C).
Transfer to a platter and serve hot with blue cheese dressing on the side if desired.