Begin by bringing a large pot of water to a rolling boil. Generously salt the water to enhance the fettuccine's flavor. Cook the fettuccine according to the package instructions until it reaches an al dente texture. Once cooked, reserve 1 cup of the starchy pasta water, then drain the fettuccine and set it aside.
In a large, deep skillet or saucepan set over medium heat, melt the unsalted butter. After the butter has fully melted, add the minced garlic and sauté for approximately 1 minute, or until fragrant, taking care not to let it brown.
Incorporate the pumpkin puree into the skillet, followed by the heavy cream. Stir well to ensure the two elements are fully combined, creating a luscious base for your sauce.
Gradually add in the grated Parmesan cheese along with the freshly grated nutmeg, salt, and pepper. Stir continuously until the cheese has completely melted and the sauce is rich, creamy, and evenly blended.
If the sauce appears too thick for your preference, gradually add reserved pasta water, a little at a time, stirring well until the desired consistency is achieved.
Gently fold the cooked fettuccine into the skillet, using a pair of tongs or a spatula to toss the pasta, allowing it to become generously coated with the creamy pumpkin Alfredo sauce.
Serve the dish hot, adorned with a sprinkle of freshly chopped parsley to add a splash of color and freshness.
Notes
For a lighter version, substitute heavy cream with half-and-half.