Bring large pot of water to a boil. Blanch the tomatoes by dropping them into the boiling water for 1 to 2 min. You will need to do them in batches. Transfer the blanched tomatoes to a sink or tub full of cold water.
Peel the tomatoes and chop them coarsely. Layer them in a large strainer with the salt. Try to use 4 tablespoons, but a bit more is okay. Much of it will run out with the water. Let the tomatoes dry for several hours or overnight, in a cool spot but not in the fridge. Don't forget to keep them a little raised from the bottom of whatever pot they're being strainer over, don't let them sit in their own water.
When you are ready to proceed, put the canning jars into a large canner with water to cover them by at least an inch and bring to a boil. Boil the jars for 10 minutes. (If you have hard water, add a shot of vinegar to the water to prevent lime build up in the jars.)
Meanwhile, peel and chop the onions, de-stem and dress the jalapenos (WEAR GLOVES!!!) and other green peppers, and peel and mince the garlic. Squeeze the juice from the limes and set aside.
Take the strained tomatoes and chop them to the texture you would like - a food processor is fine for this. Mix them with the chopped onions, garlic and chilies in a large canning kettle or other large deep pot. Chop the cilantro and mix it in, along with the ground cumin seeds.
Mix the tomato paste with a cup full of salsa. Taste the salsa and add some salt of you think it necessary. Bring the salsa to a boil. Don't change the vegetable proportions so that a safe level of acidity is maintained when canned.
Lift the sterilized jars out of the boiling water bath and empty them, half should be emptied into the sink and half back into the pot to keep the water level.
Add 3 tablespoons of lime juice to each jar. Fill each jar with salsa, to within 1/4 inch of the rims. Wipe the rims with clean paper towel dipped in the boiling water, and seal according to the manufacturers directions - i.e. by using lids boiled for 5 minutes.
Return the jars to the boiling water bath and boil them for 20 minutes, well covered by the boiling water. It will most likely be necessary to do this in batches; put as many jars into the canner as will fit. Put the jars waiting to go into the canner in a 200 degree farenheit oven to keep hot before adding to the canner. Jars that get cold will break if they get cold before being put in the boiling water.
Remove the jars from the water bath, allow to cool on a towel on a flat surface. Check the seals and label the jars.