Begin by mixing the oil and spices in a dish. Pat dry the salmon fillets. Place the fillets in the spice mixture and coat liberally. Leave the fish to marinate flesh side down.

Heat the oven to 325 degrees.

After 30 minutes, heat the cast iron skillet on medium high heat. Add 1 tbsp of the marinade to the skillet, and once shimmering, add the salmon flesh side down. Cook for 2 minutes or so - you are looking for a good blackening. Add the rest of the marinade to the skillet with the butter. Flip the fish over and add to the oven. After 8 minutes, put the skillet back on the stovetop. Spoon the marinade butter mixture over the salmon for 1 - 2 minutes.

Let the fish rest for 2 minutes. Serve over polenta and topped with Cajun spiced peppers and onions. Enjoy!