Preheat oven to 425 degrees.
Pour oil into a large rimmed baking sheet, swirling to coat. Place in oven until very hot, about 4 minutes.
Meanwhile, in a small bowl, combine mayonnaise, mustard, salt and pepper; spray 1 side of fish with cooking spray. Turn fish over; brush with mayonnaise mixture. In another small bowl, combine bread crumbs, cheese, paprika and onion powder. Sprinkle over top of fish, pressing gently. Carefully place fillets on hot oil. Drizzle fish with butter.
Bake until crumb topping is golden brown and fish flakes easily when tested with a fork, about 17 minutes. Serve with lemon wedges.