Gather all ingredients.
Mix together paprika, dry mustard, cayenne pepper, cumin, black pepper, white pepper, thyme, and salt in a small bowl.
Heat a heavy cast iron pan on high heat until extremely hot, about 10 minutes. While the pan is heating, pour 3/4 cup melted butter into a shallow dish.
Dip each fillet into butter, turning once to coat both sides.
Sprinkle both sides of fillets with spice mixture; gently pat mixture onto fish.
Working in batches, place fillets into the hot pan without crowding. Carefully pour about 1 teaspoon melted butter over each fillet. Cook until fish has a charred bottom, about 2 minutes. Turn fillets and spoon about 1 teaspoon melted butter over each.
Continue cooking until bottoms are charred, 1 to 2 minutes. Repeat with remaining fish. Serve and enjoy!