Preheat the oven to 425°F. Line a baking sheet with parchment paper and place a wire rack on top.
In a large bowl, combine buttermilk, garlic powder, onion powder, paprika, salt, and black pepper. Add the chicken pieces, ensuring they are well coated. Cover and refrigerate for at least 1 hour, or overnight for best results.
In another bowl, mix together flour, cornmeal, thyme, and baking powder. Remove chicken from the buttermilk mixture, allowing excess to drip off, then dredge each piece in the flour mixture, pressing gently to adhere.
Place the coated chicken pieces on the wire rack. Lightly spray or drizzle with cooking spray or olive oil to promote crispiness.
Bake in the preheated oven for 35-45 minutes, or until the chicken is golden brown and reaches an internal temperature of 165°F. For extra crispiness, broil for an additional 2-3 minutes at the end.
Let the chicken rest for 5 minutes before serving.