Using an electric mixer, beat butter and Parmesan until creamy. Season with a pinch of pepper.
Cook fettuccine in a large pot of boiling salted water, according to package instructions, until al dente, about 12 minutes. Reserve about 1 cup of cooking water; drain pasta.
Add fettuccine to mixer. Toss pasta with ½ teaspoon salt, cheese mixture, and ¼ cup of the pasta water. Add more pasta water as needed. Serve immediately with additional cheese.
