In a large bowl, whisk together the buttermilk, garlic, onion powder, paprika, cayenne pepper, salt, and black pepper until well combined.

Add the chicken breasts to the bowl and stir until the chicken is fully coated in the buttermilk mixture.

Cover the bowl with plastic wrap and refrigerate for at least 2 hours, or up to overnight.

Preheat the oven to 400°F (200°C). Remove the chicken from the marinade and shake off any excess.

Place the chicken on a baking sheet lined with parchment paper or aluminum foil.

Bake for 20-25 minutes or until the internal temperature of the chicken reaches 165°F (74°C).

Let the chicken rest for a few minutes before slicing and serving.

Optional: Garnish with chopped fresh herbs such as parsley, cilantro, or chives.