1. Select a 6-8 quart heavy bottomed pot. Enameled cast iron is ideal for this application but is certianly not required. Add the oil to the pot and heat it over medium high heat.
2. Add the chopped onion and garlic and saute for 3-4 minutes until the onion is translucent. We are just trying to release the oils at this point as it will cook for an hour in the sauce. Definitely do not brown the garlic or the onion. Since we are adding the onion with the garlic, it will release enough moisture so the garlic won't brown too quickly but stir frequently and keep an eye on it.
3. Select your favorite tomatoes. The ones shown below are not DOP certified San Marzanos or San Marzano tomatoes at all, but rather a plum tomato grown in the US. I like using a can of whole tomatoes added to the crushed tomatoes because I think the flavor is a little cleaner than the crushed tomatoes but the crushed add body to the sauce. You can certainly use all crushed if you prefer. Add the tomatoes to the pot. Rinse the cans with a little bit of water to get all the tomato out. The cans should be no more than 1/4 full after the rinsing. And add the rinsing water to the pot.
4. Add the basil, oregano, chile flakes and salt to the tomatoes. If someone is sensitive to hot spices, you can omit the red pepper flake. But my guess is you won't even be able to identify it is in there when this is done. It just adds a nice little something to the sauce.
5. Simmer for 60 minutes and add then add the parsley. Turn off the heat and remove the pan from the burner. We are not so much "cooking" the sauce as we might with some sauces, but rather we are trying to get a little of the moisture out of the tomatoes to thicken the sauce. Let the sauce cool. I think tomatoes taste better when they are cooled after cooking and then reheated a bit for use.