Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the pasta.

In a skillet over medium heat, melt 1/4 cup of butter. Add minced garlic and sauté for 1-2 minutes until fragrant.

Stir in the heavy cream, lemon zest, and lemon juice. Bring to a simmer and let cook for 3-4 minutes, stirring occasionally.

Add the remaining butter and Parmesan cheese, stirring until melted and combined. Season with salt and black pepper to taste.

Add the drained pasta to the sauce, tossing to coat. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.

Serve immediately, garnished with chopped parsley and additional Parmesan cheese if desired.