Pat the salmon dry. Moisture is the enemy of a good crust. Use paper towels to dry both sides thoroughly.

Mix the Cajun rub. Combine 1 tablespoon paprika, 1 teaspoon garlic powder, 1 teaspoon onion powder, 1/2 teaspoon dried thyme, 1/2 teaspoon dried oregano, 1/4–1/2 teaspoon cayenne (to taste), 1/2 teaspoon black pepper, and 3/4–1 teaspoon kosher salt. Add 1/2 teaspoon brown sugar if you like a subtle caramel note.

Season generously. Lightly brush the salmon with melted butter or oil, then coat the flesh side evenly with the spice blend. Press it on so it sticks. Leave the skin side unseasoned, or add a light sprinkle of salt only.

Preheat the pan until very hot. Use a heavy stainless steel or cast-iron skillet. Heat over medium-high until the pan is nearly smoking. Good heat is key for blackening.

Add fat to the pan. Swirl in 1–2 tablespoons butter or avocado oil. Butter adds flavor; oil raises the smoke point. A mix works well.

Sear flesh-side down first. Place salmon in the pan, spice side down. Press gently for 10 seconds to ensure full contact. Cook 2–3 minutes, until the crust is dark and crisp.

Flip and finish. Turn the salmon carefully. Cook 2–4 minutes more, depending on thickness, until the thickest part flakes easily or registers 125–130°F for medium. The skin will crisp nicely.

Rest and finish with lemon. Let the salmon rest 2 minutes. Squeeze fresh lemon over the top and sprinkle with chopped parsley or green onion.

Serve. Pair with rice, slaw, roasted corn, sautéed greens, or a simple tomato-cucumber salad.