Combine the buttermilk, Greek yogurt, lime juice, sea salt, freshly cracked pepper, crushed red pepper flakes, oregano, onion powder, and minced garlic together in a large ziplock; mix until well combined. Add the drumsticks to the marinade and place them into the refrigerator for 6-8 hours.
Take the chicken drumsticks out of the refrigerator 20 minutes prior to cooking them. Preheat the oven to 425 degrees. Line a baking sheet with tin foil then coat it with cooking spray.
Remove the drumsticks from the marinade and season with sea salt and freshly cracked pepper, to taste. Place the chicken onto the prepared baking sheet then put it into the oven. Roast the chicken for 35-40 minutes, flipping them halfway through cooking. Remove from the oven and let the meat rest for 5 minutes before serving. Enjoy!