20 lb tomatoes (about 60 medium)
1 cup chopped onion (about 1 large)
8 cloves garlic, minced
1 Tbsp olive oil
1/4 cup finely minced, fresh basil
1/4 tsp. Ball Citric Acid or 1 Tbsp. bottled lemon juice per hot jar
7 (16 oz) pint glass canning jars with lids and bands
Prepare boiling water canner. Heat jars and lids in simmering water until ready for use. Do not boil. Set bands aside.
Wash tomatoes; drain. Remove core and blossom ends. Cut into quarters. Set aside.
Saute onion and garlic in olive oil until transparent. Add tomatoes. Bring to a boil. Reduce heat and simmer 20 minutes, stirring occasionally.
Puree tomato mixture in a food processor or blender, working in batches. Strain puree to remove seeds and peel.
Combine tomato puree and basil in large saucepot. Bring to a boil. Reduce heat and simmer until volume is reduced by half, stirring to prevent sticking.
Add 1/4 tsp Ball Citric Acid or 1 Tbsp. bottled lemon juice to each hot jar (this will make the tomato sauce acidic enough to use hot water bath method.) Ladle hot sauce into hot jars leaving 1/2 inch headspace. Remove air bubbles. Wipe rim. Center hot lid on jar. Apply band and adjust until fit is fingertip tight.
Process filled jars in a boiling water canner for 35 minutes, adjusting for altitude. Remove jars and cool. Check for seal after 24 hours. Lids should not flex up and down when center is pressed.