Prepare your water bath canning pot or your steam canner. Fill the water bath canning pot with water, add 7-pint jars, and bring to a boil OR fill the steam canner to fill line and turn on low with the 7-pint jars nearby on a towel-covered countertop.
Blend the tomatoes. Start on the "food chop" setting, and then move to a medium blend setting, for up to two minutes or until the visible skin pieces in the blender are smaller than half an inch.
Combine olive oil, garlic, and onion in the bottom of a preserving pan at medium-low heat and cook till onion is soft. Add salt and pepper.
Pour the blended tomato smoothie on top of the cooked garlic & onion mixture and stir to combine. Repeat the blending process until all tomatoes are blended and added.
Cook on medium heat until sauce is reduced, darker red in color, about 1 hour.
Ladle into jars one at a time, maintain 1/2 inch headspace, add 1/2 teaspoon citric acid to each jar, apply lids and rings, and either submerge into the boiling water of the boiling water bath with a jar lifter OR set gently on the rack of the steam canner.
Process for 25 minutes PLUS 5 minutes for every 1000 ft above sea level. Remove from heat, rest jars carefully on towel covered countertop. Label cooled jars and store for up to 1 year. Yields 8-10 pints.
