Start by cooking the fettuccine pasta according to package instructions. Once done, reserve ½ cup of pasta water, drain the rest, and set aside.
While the pasta cooks, season each salmon fillet generously with Cajun seasoning, salt, and pepper.
In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Once hot, place the salmon fillets skin-side down. Cook for about 4-5 minutes on each side, or until cooked through and golden brown. Remove the salmon from the skillet and set aside to cool slightly, then flake into large pieces.
In the same skillet, add the remaining tablespoon of olive oil, and sauté minced garlic for about 30 seconds until fragrant.
Add the halved cherry tomatoes and cook for 2-3 minutes until slightly softened.
Pour in the heavy cream and bring to a simmer. If the sauce is too thick, stir in some of the reserved pasta water to reach your desired consistency.
Add the spinach leaves and cook for 1-2 minutes until wilted. Add salt and pepper to taste.
Toss the cooked fettuccine in with the creamy mixture until well coated. Gently fold in the flaked salmon and Parmesan cheese until combined.