Starchy pasta water is often incorporated into sauce to silk-ify the texture and help it stick to the spaghetti. The more starch, the creamier the sauce. You can use this principle to take your plate of pasta to a dreamier place, and "super starch" it by adding a handful of semolina flour to the cooking water. Photo by Erik Statten.
This trick from Epicurious works for any type of sauce, dairy-free or dairy-ful. Just toss in your flour before even adding the pasta and cook as normal. Reserve about half a cup of this super-starchy elixir, and drain. Then it's time to bring everybody together, mixing pasta, sauce and water in a skillet and bringing it all to a simmer. Cook until sauce thickens and coats your pasta noodles, tossing with tongs every couple of minutes to help everything emulsify.