If you're already sauteeing the veggies, then you're halfway there. I make a homemade sauce with Unico crushed tomatoes. I think there might be salt added but no sugar.
I sautee onions, garlic, peppers and mushrooms. (or whatever you like!) When they're nice and soft I add two cans (you get a nice big pot of sauce) of Unico crushed tomatoes (my husband thinks they taste the best) and cook for between 30 minutes and two hours..depending on how much time I have. Add any seasonings you like, we just use a lot oregano and, if you like the sauce a bit sweet, add some Splenda. You can eat it as is, make it a meat sauce or we just add Yves Just Like Ground. Makes a huge pot, tastes like a really good, thick, meat sauce and is really healthy.
I like this sauce so much that I can eat it as is, but it's nice over a small amount of whole wheat pasta.
Hope this helps and if you try it, let me know if you like it!