Core and chop the tomatoes into bite-sized pieces. Place them in a large glass mixing bowl.
Core the peppers, removing the seeds and membranes. Dice the peppers.
Add peppers to the tomatoes.
Chop the onions and add them to the tomato and pepper mixture.
Add the 1-1/2 cup of lemon juice.
Add 3 TBS of canning salt.
Add the mixture to your cooking pot & bring to a boil.
Simmer for 3 minutes, then set aside.
Fill the jars leaving 1/2 inch headspace.
Remove air bubbles using the bubble freer spatula.
Place the lid on top of the jar & tighten the rim.
Place the canning rack down in the pot. Fill to about 1/3 full.
With the jar tongs, lower the full jars into the hot water, careful not to tap them together in the process.
Once the jars are in the pot, add enough hot water to cover the jars by about 2 inches. CAUTION: Do not, at any point, allow cold to touch the hot glass jars, or they will shatter!
Boil for 15 - 25 minutes depending on your elevation.
When they are finished cooking, carefully remove them to a rack that is out of any draft.
Set aside for 12-24 hours to let the seal form. You'll start to hear little dings as the seals take.
Double check the seal before storing.