In a large pot of boiling salted water, cook the fettuccine according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta and set aside.
In a large skillet over medium heat, melt the butter. Add the minced garlic and sauté for about 1 minute until fragrant.
Stir in the pumpkin puree and heavy cream, mixing well. Let it simmer gently for about 3-4 minutes, stirring occasionally.
Gradually add the grated Parmesan cheese, nutmeg, cinnamon, salt, and pepper. Continue stirring until the cheese melts and the sauce is smooth and creamy.
Add the cooked fettuccine to the skillet with the sauce. Toss to coat the pasta evenly. If the sauce is too thick, add a little reserved pasta water until the desired consistency is reached.
Plate the creamy pumpkin Alfredo pasta and garnish with freshly chopped parsley.