Boil a large, well-salted pot of water for the pasta. Cook al dente as directed.
Meanwhile, add the butter, lemon zest and lemon juice, minced garlic, white wine, cream, and Italian seasoning to a skillet over medium-high heat. Let the sauce bubble for 5 minutes.
Gradually add the flour to sauce, stirring/whisking constantly to ensure sauce is smooth.
Stir in the parmesan cheese.
Continue to simmer the sauce on medium heat for an additional 5 minutes, stirring frequently. The sauce should be noticeably thickened by now. If not, continue simmering it for a few more minutes.
Add shrimp and continue to cook for an additional 5 minutes until sauce is thickened as desired and shrimp are cooked.
Drain the spaghetti (reserve a tablespoon of the pasta water and add it to the sauce), then toss the pasta with the sauce. Sprinkle with fresh parsley. Serve immediately.