Bring a large skillet of water to a boil over high heat. Add salt and fettucini cooking until al dente, and toothsome. The pasta should still have a little bite to it or a white line in the center when bitten into. Reserve 1/2 cup of pasta water and drain pasta in a colander. Place pasta back in pan.
Over low heat add butter and Parmigiano in stages stirring slowly and gently to allow the heat and agitation of pasta to emulsify the sauce. Add a little bit of pasta sauce to create a creamier consistency if the cheese thickens the mixture too much.