Gather all ingredients.

Set an oven rack about 6 inches from the heat source and preheat the oven's broiler. Line a baking sheet with aluminum foil; spray with cooking spray.

Arrange haddock fillets on the prepared baking sheet.

Mix onion powder, paprika, garlic powder, black pepper, salt, and cayenne pepper in a small bowl; sprinkle seasoning over fish, then dot with butter.

Broil in the preheated oven until fish flakes easily with a fork, 6 to 8 minutes.

Serve with lemon wedges. Enjoy!