Cook the pasta according to package instructions to al dente, drain, reserving 1 cup of the water, and return the pasta to the pan, covered to keep warm.
Use a large skillet on medium heat and add the butter, garlic and lemon zest. Cook for about a minute to allow the garlic to get fragrant.
Add 1 tablespoon of flour and stir it into the oil and cook for at least a minute to get rid of the flour taste. Then, add the milk while whisking to prevent lumps. Allow this to come to a boil to thicken, (3 minutes).
Add the cream cheese and whisk it in to melt. (You can cut this up into pieces and it will melt in faster). Then add the grated Parmesan and whisk until melted.
Add the reserved pasta water a little at a time while stirring to thin the sauce to your desired consistency. I added about 3/4 cup. Then add the pasta to the sauce and toss to combine. Give the sauce a taste and add salt and pepper as desired. I added about 1/2 teaspoon of Diamond Crystal Kosher salt and quite a few grinds of fresh black pepper. Top with chopped parsley if desired.
Notes
Serve the Fettuccine Alfredo by itself with a vegetable and some sturdy bread. You could also combine with some cooked shrimp or bay scallops. Yum. Slices of chicken breast or pork tenderloin on the side would also be excellent.