In a small bowl, stir together paprika, thyme, garlic salt, onion powder, mustard, and red pepper. In a shallow dish, pour melted butter. Dip fish in melted butter; sprinkle with paprika mixture.
Heat a large cast-iron skillet over medium-high heat. Add fish, in batches if necessary, and cook until fish flakes easily with a fork, 5 to 6 minutes per side. Serve with Pineapple Relish.
Recipe by Southern Lady Magazine at https://www.southernladymagazine.com/blackened-grouper-pineapple-relish/