1. Mix together the onion powder, thyme, cayenne pepper, cumin, coriander, salt, and pepper in a small bowl.
2. Brush fish fillet with melted butter then rub with spice mixture, covering all sides. let sit for at least 30 minutes.
3. Arrange the fillets in the basket of your Air Fryer. Set the temperature to 400 F (200 C) and cook for 15 minutes or until golden brown and cooked through.