Cook the Fettuccini: Crank up the heat to high under your heavy cast-iron skillet, adding the 6 cups of water and a good shake of salt. Once it hits a rolling boil, drop in the pasta and let it cook for around 8 minutes. You want it just shy of fully cooked, as it will soften up more while baking. Drain it well, move it into a medium mixing bowl, and set it aside for a moment.