This is how my mother taught me to make tomato sauce. She use to use fresh tomatoes and boiled them to pop the skins and all but found this was a whole lot easier, added perk, we all loved it. This is also a good use for left over, cooked, pork chops, or beef even chicken. Just throw it in and let it simmer in there. Left over meats will flavor the sauce nicely. (of course meatballs and/or sausages are always welcomed)
Pour the tomatoes into a large pot. Take the cans and using hot water, fill up about half way, try to scrape sides to get whatever tomato is still clinging. Add that to the pot. (Remember to fill up the can about half way, you don't want too much water. If you need to, extra water can be added later)
Add the paste into the pot. Using hot tap water fill the paste can and scrape off any clinging paste. Add to the pot.
Throw in the rest, (nope, we don't fry the garlic) and simmer, stirring often. (NOTE: if you will be adding in meat, go ahead, it will only flavor the sauce more. Be sure the meat is cooked first though)
Check as the sauce cooks down it will thicken, so you may need to add in a bit of water to get it to the thickness you like.
When the onion is cooked through, soft and just about falling apart, your sauce is done. This sauce takes a couple of hours to make, but well worth the time and stirring.