Preheat your oven to 400 degrees.
Mix the dry ingredients together in a flat bowl. Dip one piece of fish in lemon juice mixed with the melted butter, then dip in the dry mixture until well coated. Continue until all pieces are coated. Place on a clean, dry plate.
Meanwhile make the pineapple salsa, mixing all ingredients together in a bowl.
Heat a large skillet lightly greased with olive oil or avocado oil on medium high heat. When the pan is hot, place each piece of fish in the skillet and brown each side for 2 minutes. Next transfer the skillet to the oven and finish cooking for 6-8 minutes more or until it flakes when checked on the edge with a fork.
Serve with pineapple salsa on top of the fish or alongside the fish in a bowl. The coolness of the salsa is a compliment to the spiciness of the blackened fish.