1. Brush each fish fillet liberally with melted butter.
2. Combine spice mix, paprika and chili powder and using your hands, rub spice mixture evenly over fillets.
3. Heat a large cast iron frying pan over a high heat until very hot. Add fish fillets and cook for 1-2 minutes each side or until fish flakes when tested with a fork. Serve immediately with any remaining melted butter.