I don't know a good pizza sauce but I recently saw a low calorie/on plan pizza-kinda-thing on Food Network. I made it, and even my husband, who is not "on diet" loved it a lot! Here it is:
You take a 5-inch pita, spread a heaping tablespoon of canned crushed tomatoes on it (I drain them a bit), and then you layer 2-3 very thin red onions slices, few tomato slices, roasted peppers (if you have some left from the last bbq), sprinkle with half-salt, pepper and oregano, and then instead of a regular cheese (mozarella or whatever) you put 4-5 tablespoon scoops of light ricotta cheese (about 1/2 c in total) on top of your pizza.
To the 350F oven it goes, for about 8-10 minutes. It's a fast lunch, I count as 1S, 1 P and 1-1/5 V.
It is a very simple and fast pizza (pita-pizza)