Bring a large pot of salted water to a boil and cook the fettuccine according to package directions until al dente.
Reserve about 1/4 cup of the pasta cooking water, then drain the pasta in a colander.
Return the drained pasta to the pot over low heat, add the cauliflower sauce and 1 to 2 tablespoons of the reserved pasta water if needed to loosen the sauce, and stir until evenly coated.
Stir in the grated Parmesan and adjust seasoning with salt and pepper to taste.
Serve immediately, sprinkled with additional Parmesan and chopped parsley.
