• Add the oil, onions and garlic to a heavy-bottomed stockpot (to help prevent scorching) over medium low heat.
• Cook for 10-15 minutes, stirring frequently, until the onions are softened and mostly translucent. Do not brown the onions and garlic.
• Stir in the remaining ingredients.
• Bring to a simmer (gently bubbling state) and cook, uncovered, over low heat for 30 minutes.
• Remove the pan from the heat and let cool slightly before blending until smooth, using either a stick (immersion) blender or a standard blender.
• You can either split into 1-cup portions to freeze, transfer to a jar with a tight fitting lid for refrigerator storage, or proceed on to canning the sauce...

To Boiling Water Bath Can the Sauce for Shelf Storage:

• Fill sterile canning jars to within 1/4-inch of the top.
• Wipe the rims with a paper towel dipped in vinegar.
• Lay clean, new lids on the jars and screw on the rings to finger-tip tightness.
• Place in a canner with water to cover the lids by 2-inches.
• Bring to a boil, with the lid in place, and boil for 30 minutes for pint jars and 40 minutes for quarts.
• Turn off the heat and let the jars rest in the water for 5 minutes before carefully transferring jars to a cooling rack to rest for 24 hours.
• Remove rings, wipe jars, label and store in a cool, dry place for up to a year.

To Pressure Can the Sauce for Shelf Storage:

• Fill sterile canning jars to within 1-inch of the top.
• Wipe rims with a paper towel dipped in vinegar.
• Place lids on jars and screw on rings to finger-tip tightness.
• Place in a pressure canner according to your manufacturer's instructions.
• Process at 10 pounds of pressure for 20 minutes for pints and 25 minutes for quarts.
• Allow the pressure canner to come back to atmosphere naturally. (Do not cool canner by pouring water over it.)
• Transfer the jars to a cooling rack to rest for 24 hour hours.
• Remove rings, wipe jars, label and store in a cool, dry place for up to a year.