Fill your water-bath canner cool water and begin heating it up on the stove.
Cut the green tomatoes, onions, and green peppers into small dice. Finely chop the cilantro (if using).
Combine the chopped vegetables, cilantro, lime juice, salt, and spices in a large pot over medium-high heat. Stir occasionally.
Once the veggies have softened, use an immersion blender to finely mince the veggies. You're looking for tiny, uniform pieces rather than a smooth puree. Reduce heat and simmer the sauce for 5 minutes.
Fill your clean jars with hot water to heat them for the next step.
Once the sauce has thickened slightly and your canning jars are hot, ladle the sauce into the clean, pre-warmed jars, leaving a 1/2 inch headspace. Debubble each jar. Wipe the rims clean, then place lids on each jar and secure with a ring until fingertip-tight.
Carefully lower the jars into the water-bath canner. Remember: Water must cover the tops of the jars by at least 1 inch. Bring the water to a rolling boil, cover, and process for 25 minutes.
After 25 minutes, turn off the heat and let the jars sit in the canner for an additional 5 minutes. Remove the jars from the canner and place them on a towel-lined countertop. Leave them alone for at least 12 hours to cool.
Test the seals. The lid centers should be depressed and should not "pop" when pressed. Unscrew the rings and lift each jar by the lid. It should feel firmly stuck on. Any jar that didn't seal should go in the fridge and be used within a week.