I used to use the tomato basil Ragu Light, which used to be labelled as fat free (although I haven't found it recently). It was totally vegan (even listed "natural vegetable flavorings" on the label. I think they may have changed the formula as the ones I've seen in the store recently are labelled as lowfat not fat free. At any rate, plain pasta sauce is So easy to make yourself and only takes as long as the noodles take to cook. Here is how I make mine:

Simmer until heated through. Tomato paste will thicken the sauce. You may want to add it 1 T. at a time so you get the desired thickness. This is really tasty, super quick, and totally fat free. If you want other stuff in it, just steam some veggies in the microwave (or use leftovers out of the refrigerator) and add them to the sauce.