Bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve about half a cup of pasta water before draining. This starchy water helps adjust the sauce later.
Heat olive oil in a large skillet over medium heat. Season the salmon lightly with salt and pepper, then cook for 3–4 minutes per side until just cooked through. Remove and set aside.
In the same skillet, add chopped shallot and cook until soft and translucent. Stir in the garlic and cook briefly until fragrant, being careful not to burn it.
Lower the heat and pour in the heavy cream and milk. Stir gently, allowing the mixture to warm and thicken slightly. Add Italian seasoning and black pepper.
Stir in the sliced sun-dried tomatoes, then add fresh spinach. Let the spinach wilt naturally into the sauce, which takes about a minute.on
Add the cooked pasta directly to the skillet, tossing gently to coat it in the sauce. Flake the salmon into large chunks and fold it in carefully.
Sprinkle in freshly grated Parmesan cheese and stir until melted. Use reserved pasta water if needed to loosen the sauce to your desired consistency.