Cook the fettuccine according to package instructions. When done al dente, reserve 1 cup of pasta water, drain the pasta, and put the pasta back in the pan.
Add the butter, add the lemon juice, half of the lemon zest, and mascarpone. Mix well and adjust the mascarpone or lemon to your liking. If dry add some of the cooking water.
Serve on pasta dishes and sprinkle the remainder of the lemon zest
Giangi's Kitchen provides nutritional information, but these figures should be considered estimates, as a registered dietician does not calculate them.