In a medium bowl, combine 1/2 teaspoon kosher salt, 1/2 teaspoon sweet paprika, 1/2 teaspoon poultry seasoning, 1/4 teaspoon garlic powder, and 1/8 teaspoon freshly ground black pepper; add the chicken drumsticks and turn to coat.
Pour 1 cup buttermilk and the juice of 1/2 lemon over the seasoned chicken, cover, and refrigerate for 6–8 hours or overnight.
Preheat the oven to 400°F (200°C). Place a rack on a baking sheet and lightly spray the rack and sheet with cooking spray.
In a shallow bowl, mix 2/3 cup panko, 1/2 cup crushed cornflakes, 2 tablespoons grated Parmesan, 1 1/2 teaspoons kosher salt, 1 teaspoon dried parsley, 1 1/2 teaspoons sweet paprika, 1/2 teaspoon onion powder, 1/2 teaspoon garlic powder, and 1/4 teaspoon chili powder.
Remove a drumstick from the buttermilk, let excess drip off, then dredge it in the crumb mixture to coat completely; repeat with remaining pieces.
Arrange the coated drumsticks on the prepared rack, spray the tops lightly with cooking spray, and place the baking sheet in the oven.
Bake until the coating is golden brown and the chicken is cooked through, about 40–45 minutes, turning if desired for even browning.
