Heat 2 quarts of water in a 4 quart kettle (or fill whatever pot you use with enough water to cover tomatoes) to boiling

Working in batches, blanch tomatoes for about 45 seconds each to loosen skins. When tomatoes are properly blanched, you may see some skin bread and curl. The skin will easily pull off of the flesh.

After blanching tomatoes, rinse with cool water, and peel. You may need to poke it with a knife to break the skin and get started, but a property blanched tomato should release its skin with no more than hand pressure. 

Remove the hard core from the center of your tomatoes, and then dice into whatever size pieces you prefer. I often for for a more “petite diced” size since my kids don’t love big chunks. For large batches, you can give the tomatoes a quick whirl in the food processor if you prefer, and don’t mind uneven chunks, and possibily a lot of pulverization. 

Prepare jars and canner.

In each pint jar, add 1/4 teaspoon citric acid, or 1 Tablespoon of bottled lemon juice (double for quarts, halve for half pints, etc.)

Ladle diced tomatoes into jars, leaving 1/2 inch headspace. Top with water if tomatoes haven’t produced enough liquid to cover themselves. 

Wipe rims of jars with a damp cloth or paper towel to clean and remove debris.

Screw down lids and rings firmly.

Pack into prepared canner, ensuring that water in canner covers the jars by a depth of at least 1 inch. 

Heat over medium-high heat to a rolling boil. 

Process pint jars for 40 minutes, or quart jars for 45 minutes. 

Remove from heat, and remove cover. 

Let jars cool in water for 30+ minutes, before remove from canner. 

When removing hot jars from canner, it is wise to cover them with a towel until they are substantially cooled. 

Let rest for 24 horse. Check for seal, wash jars if needed (mine always have hard water residue on them), and store in a cool place out of direct light.