Place chicken in a shallow dish, cover with buttermilk, and toss to coat. Cover and refrigerate for at least 2 hours or overnight.
Preheat oven to 200°C (400°F). Line a baking tray with parchment and lightly grease it.
Mix flour with paprika, garlic powder, onion powder, thyme, basil, salt, pepper, and cayenne (if using).
Lift chicken from buttermilk, let excess drip off, then coat well in the flour mixture. Shake off any extra.
Place chicken on the tray with space between. Spray or brush with oil or melted butter.
Bake 40–45 minutes, flipping halfway, until golden and cooked through (75°C / 165°F inside).