Boil a salted pot of water and cook the pasta al dente according to package directions.
Meanwhile, season the salmon with salt & pepper.
Add butter to a skillet over medium-high heat. Once the pan is hot, add the salmon and cook it for 2 minutes/side, then take the fish out of the pan and transfer it to a plate (do not fully cook the salmon).
Reduce the heat to medium. Add the garlic, Italian seasoning, wine, and lemon juice/zest to the skillet and let it bubble for about 30 seconds.
Stir in the cream.
In a small bowl, mix the cornstarch with 1 teaspoon of cold water and stir it into the skillet.
Once the sauce starts to bubble a bit, add the salmon and parmesan to the sauce. Break the fish up with your spoon into bite-size pieces. Cook for a few minutes until the salmon is cooked through and the sauce has thickened up more.
Stir in the spinach and let it wilt.
If the sauce gets too thick, reserve some of the hot pasta water and add it to the sauce.
Once the pasta is cooked, drain it, add it to the skillet, and toss it with the sauce. Season with more salt & pepper as needed. Serve with extra grated parmesan cheese if desired.