Mix Spices together in a small sealable bag or container; transfer 1 tablespoon spices to a large freezer bag. To the large bag, whisk in buttermilk, Dijon and egg. Add chicken and marinate 1 hour at room temperature or up to 12 hours in the refrigerator. Store remaining spices separately.
When ready to cook or anytime while the chicken is marinating, spread panko into an even layer on a baking sheet. Spray with cooking spray. Bake at 400 degrees F for 5 minutes or until lightly golden.
Transfer toasted panko to a wide shallow bowl and whisk in Parmesan, flour, cornmeal and remaining spices.
Preheat oven to 400 degrees F. Place a rack on a foil-lined baking tray and spray with cooking spray.
Working in batches, remove chicken tenders from buttermilk and dab off excess marinade with paper towels then add to the breadcrumb bowl. Coat the chicken with a clean hand, pressing the breadcrumbs into the chicken.
Transfer breaded chicken to the prepared baking rack. Repeat with remaining chicken. Drizzle chicken with melted butter.
Bake at 400 degrees F for 12-18 minutes (18 only if tenders are large) then broil for 5-10 minutes until crispy, without moving the oven rack.
Serve with desired dip of choice.