In a bowl, beat the softened butter, grated Parmesan, and garlic powder with a hand mixer until smooth and creamy.
Bring a large pot of salted water to a boil and cook the fettuccine according to the package directions until al dente, about 12 minutes.
Reserve 1/2 cup of the pasta cooking water, then drain the pasta in a colander.
Return the hot fettuccine to the warm pot and sprinkle with 1/2 teaspoon salt.
Toss the pasta with the cheese-and-butter mixture and 1/4 cup of the reserved pasta water until the sauce coats the noodles; add more pasta water as needed to reach a creamy consistency.
Serve immediately with additional grated Parmesan cheese, if desired.
