1. Bring a large pot of salted water to a boil and cook the pasta until al dente. Reserve 1/4 cup pasta water, then drain the pasta.

2. Pat the salmon dry and season it with salt and black pepper.

3. Heat olive oil in a large skillet over medium heat. Cook the salmon for 4 to 5 minutes per side, or until cooked through. Remove it from the skillet and flake into large pieces.

4. In the same skillet, melt the butter and cook the garlic for 30 seconds until fragrant.

5. Stir in the lemon zest and lemon juice.

6. Pour in the heavy cream and cook gently for 1 to 2 minutes.

7. Add the Parmesan cheese and stir until the sauce is smooth.

8. Add the cooked pasta, spinach, and reserved pasta water. Toss until the spinach wilts and the pasta is coated.

9. Gently fold in the salmon and sprinkle in the red pepper flakes and parsley.

10. Taste and adjust seasoning, then serve warm with extra Parmesan if desired.