Prep the jars. Wash your pint or half-pint jars and keep them hot until you fill them. Prepare your lids and bands according to the manufacturer's directions. Fill your canner and start heating the water.
Peel the tomatoes. Dip washed tomatoes in boiling water for 30 to 60 seconds, until the skins split. Move them straight into cold water, then slip off the skins. Core them, remove the seeds, and chop into ¼ to ½ inch pieces. Measure 6 cups.
Prep the onions and peppers. Peel and dice the onions. Remove seeds and membranes from bell peppers. For hot chilies, remove the stems and keep or remove as many seeds and membranes as you like for heat. Dice everything into ¼ inch pieces and measure level in dry measuring cups for exactly 9 cups total. Wear gloves for the hot chilies.
Cook the salsa. Combine the tomatoes, onions and peppers, bottled juice, salt and any dried seasonings in a large pot. Bring to a boil over medium heat, stirring. Reduce the heat and simmer 3 minutes, stirring to keep it from scorching.
Fill the jars. Ladle the hot salsa into the hot jars, leaving ½ inch headspace. Remove air bubbles and adjust the headspace back to ½ inch if needed. Wipe the rims with a clean damp paper towel. Apply lids and bands, fingertip tight.
Process. Set the jars in the canner with water covering them by at least 1 inch. Bring to a full rolling boil, then start your timer. Process half-pints or pints for 15 minutes at 0 to 1,000 feet elevation, 20 minutes at 1,001 to 6,000 feet, or 25 minutes above 6,000 feet.
Cool and check seals. Turn off the heat, remove the canner lid, and let the jars rest 5 minutes. Lift the jars onto a towel, 1 inch apart, and let them cool undisturbed for 12 to 24 hours. Check that each lid is sealed and curves down in the center.