Place the chicken tenders in the buttermilk and marinate for at least 30 minutes or up to 8 hours.
Preheat the oven to 425 degrees. Place an empty sheet pan in the oven for 10 minutes.
On a large plate, mix together the flour, cornmeal, panko breadcrumbs, salt, pepper, onion powder, garlic powder and smoked paprika.
Take each chicken tender out of the buttermilk mixture and place on the plate with the flour mixture; turn evenly to coat. Repeat with remaining chicken.
Remove the sheet pan from the oven and place the butter on it. Wait 2-3 minutes until butter is melted. Swirl the butter around the pan until the bottom is evenly coated.
Place the chicken in a single layer on the melted butter. Bake for 10 minutes then flip. Bake for 8 minutes more. Broil for 2-3 minutes or until tops are crispy. Serve immediately, sprinkled with parsley if desired.