Wash canning jars in hot, soapy water or in the dishwasher.
Set pressure canner on burner. Cover the bottom of canner with 2-3” water.
Place canning jars in the canner to sterilize. Cover. Place pressure weight on canner to create steam. Steam jars for about 5 minutes to sterilize. Remove from heat and allow pressure to reduce. Remove weight. Open canner to remove jars.
3. Prepare tomatoes
Wash tomatoes. Cut out bruises, cracks, and bad spots. Cut out center stem.
Quarter tomatoes. Process them in food processor in short bursts or slow speed to chop into chunks. (High speed whips air into the tomatoes, creating unnecessary foam.) Or, use a tomato pressto save time and work, eliminate chopping, and reduce waste.
Pour chopped tomatoes into a heavy pot.
Repeat first three steps until all tomatoes are chopped.
Add salt to taste – about ½ teaspoon per quart.
Cook tomatoes on medium to high, stirring regularly, until tomatoes reach a slow boil.
4. Prepare lids and rings
While tomatoes are cooking, place jar lids and rings in a pot, covering them with 2-3 inches of water. Bring water to a boil to sterilize lids and rings. Remove after 3-5 minutes.
5. Pack jars
Place tomato strainer or colander in the sink, straddling a large pot. Pour cooked tomatoes through strainer to remove excess juice. Set aside tomato juice to can.
Place wide-mouthed funnel on top of a sterilized jar. Pour tomatoes through the funnel to fill the jar. Leave ½” space at the top of the jar. Insert a knife into the jar. Run it around the bottom of the jar to release any air pockets. Repeat packing process with rest of jars and tomatoes.
With a clean, damp paper towel, wipe jar rim. Place lid on jar rim. Wind ring around jar top to secure lid. Tighten. (Be careful; if you over-tighten lids, they are difficult to remove when you’re ready to use tomatoes.)
6. Cook tomatoes
Place filled jars in the pressure canner or hot water bath. Follow manufacture’s directions. Secure lid. Cook on high until canner releases some steam, and then place weight on vent.
Allow pressure to heat to between 5 and 10 pounds. Cook for 10 minutes.
Remover the pressure canner from the heat. Allow pressure to reduce. Vent weight.
Remove lid. Carefully lift jars out of canner and onto a heat-resistant surface.
7. Cool and store
Let jars cool. Avoid tightening rings or you may break the seals.
As jars cool, you may hear lids seal securely with a telltale “pop.”
Test seals by pressing down the center of lids. If centers are firm or concave (or if you heard them pop), lids are sealed.
Leave rings on cooled jars or remove rings and use them for your next batch. Sealed lids will keep tomatoes preserved.
Store canned tomatoes in the pantry or other dry area.