Cook pasta according to package instructions in salted water. Drain and set aside.
Season salmon fillets with 1 teaspoon of Cajun seasoning, on both sides.
Heat up oil in a large skillet. Cook salmon until seared and mostly cooked through, 3-4 minutes per side. Transfer to a plate, flake with 2 forks and set aside. You can also flake the salmon right before serving.
To a now empty skillet, add butter, chopped shallot and minced garlic. Cook for 1-2 minutes, until fragrant.
Add white wine and cook for about 5 minutes to reduce.
Pour in heavy cream, stir and cook for about 1 minute. Add arugula, lemon juice and the remaining 1 teaspoon of Cajun seasoning. Stir and cook for another 1-2 minutes, until arugula wilts.
Add cooked pasta to the sauce and toss to coat.
Add flaked salmon, garnish with parsley leaves and season with salt and pepper, if needed.
Serve and enjoy, preferably with a glass of white wine.