Working in small batches, dunk clean tomatoes in boiling water for 30-45 seconds, to just loosen or crack the skin
Immediately remove, and let cool while you dunk the next batch
Remove skin (it should slip right off), and core tomatoes
Dice, or to make large batches quickly, whirl in the food processor
Pack into sterilized jars to within ½ an inch of the lid
For each pint add 1 Tablespoon of lemon juice, or ¼ teaspoon of citric acid
Wipe rims clean, and fit with lid and ring
Fit inner rack inside of canning kettle and fill about half full of cool or lukewarm water
Add jars and begin heating
Bring to a rolling boil, and continue boiling for 40 minutes
Remove from heat. If you have the time, just let the whole kettle cool with the jars of tomatoes inside.
If you don’t, remove the lid and let cool for 10 minutes, then carefully remove jars from kettle, keeping them away from drafts. Cover hot jars with a bath towel to protect them from drafts (and breakage drafts can cause) as they cool.
Leave rings on jars at least 24 hours before removing to store jars in a cool, dark place until ready to use.