Cook garlic, onion, red pepper flakes, and oil in a medium saute pan or skillet on low heat for 5 minutes or until onions are translucent. Stir frequently to avoid burning the garlic.
Add tomato paste and cook for another 3 minutes or until the color begins to darken.
Add the plum tomatoes and gently break them apart with a wooden spoon or spatula, then stir in oregano, basil, bay leaf, balsamic vinegar, salt, and pepper.
Allow the sauce to simmer on low for fifteen minutes and check for seasoning. Additional simmer time may be added if you want your sauce to be thicker. If you want it to be thinner, add a little water at a time.
You can further puree the sauce in a food processor or blender to your desired consistency or keep it chunky.
Sauce can be cooled and refrigerated for up to five days in an airtight container.
Video
Notes
It is important to maintain low heat during the entire process to avoid burning the garlic. Cooking the tomato paste until it darkens is an important step that will add incredible depth to the flavor of the sauce.