This dish absolutely requires the pasta be fresh in order for it to stand up to the rich cream sauce.
In a large, heavy skillet, stir 1 cup of the cream and the lemon juice to blend.
Add the butter and cook over medium heat, stirring occasionally, just until the butter melts, about 3 minutes.
Stir in the lemon zest and nutmeg.
Remove from the heat.
Meanwhile, bring a large pot of salted water to a boil.
Add the fettuccine and cook, stirring occasionally, until tender but still firm to the bite, about 4 minutes.
Add the pasta, the remaining ½ cup of cream, the Parmesan, and ¼ teaspoon each of salt and pepper to the cream sauce in the skillet.
Toss over low heat until the sauce thickens slightly, about 1 minute.
Season with more salt and pepper to taste.
Transfer the pasta to wide, shallow serving bowls and serve immediately.