Preheat oven to 450°F. Line a large, rimmed baking sheet with aluminum foil and place a wire rack on top. Coat the rack with cooking spray.
Place buttermilk in a shallow dish.
In a separate shallow dish, combine cornmeal, seasoned salt, pepper, garlic powder, onion powder, paprika, and cayenne pepper.
Pat fish dry with a paper towel. Season with salt and pepper, to taste.
Working with one piece of fish at a time, dip a catfish fillet in the buttermilk mixture, and shake off any excess.
Transfer buttermilk-soaked fish to the cornmeal mixture and gently roll to coat on both sides.
Repeat with remaining fillets.
Arrange the fish about 1-inch apart on the prepared wire rack. Coat the tops of the fillets with cooking spray.
Bake until crispy and golden and the fish flakes easily with a fork, about 15-20 minutes, turning the fillets over and coating with cooking spray again on the opposite side halfway through. Serve with tartar sauce, lemon wedges, and fresh parsley.