Bring a large pot of water to the boil and add salt.
Once the water is boiling, cook the Fettuccine according to the package instructions. Once the pasta is cooked, reserve about 1 cup of cooking water then drain.
In the meantime, melt the butter in a large skillet over medium heat and season with salt and pepper.
Toss the drained Fettuccine in the pan together with the butter. Add the reserved cooking water, Parmigiano Reggiano, then toss the pasta until coated in sauce. Serve immediately.