cook in the liquid from the dressing.
Bake on the center rack for 35 to 40 minutes. Carefully remove the foil and check a piece of macaroni from the center of the pan; it should be just tender. If the pasta still seems a bit firm and looks dry on top, pour up to 1/2 cup water evenly over the pasta, re-cover with foil, and bake for another 10 minutes.
Once the pasta is tender and most of the liquid is