Preheat your outdoor grill to medium-high heat or heat a grill pan on the stovetop over medium-high.
Brush the salmon fillets lightly with olive oil. Rub Cajun seasoning all over the fillets, coating both sides. Adjust salt if needed.
Place the salmon fillets skin-side down on the grill. Cook for about 4–5 minutes on the first side without moving them, until grill marks form. Flip carefully and cook for another 3–4 minutes, or until the salmon easily flakes with a fork.
Transfer the grilled salmon to plates. Garnish with lemon slices and fresh parsley. Serve immediately.