This is a very versatile sauce that I use in soups, pastas, or as a pizza base. I make mega-batches this time of year when roma tomatoes are ripe. I have 2 large broiler pans that came with my gas range, and alternate them through the oven--when it's really hot I do the roasting in my barbecue!
For each broiler pan, I use about:
15 ripe roma tomatoes (more if they're small!), washed, cut in half
1/2 a large onion, chunked
5 cloves of garlic, peeled
A good drizzle of olive oil
Salt and Pepper
Run your hands through it so everything is well coated with oil.
Then roast for 30-40 minutes at about 375. You want the edges to be browning a bit, and for the aroma of ROASTED veggies to come through. Give them a stir every 10-15 minutes.
Then I just scoop the mess into my blender and give it a whiz.
From there I pour the sauce into canning jars and process in hot water bath for 30 minutes. Or you could always freeze the sauce.