Prep. Before you begin, make sure you have clean jars, lids, and bands. Sterilize the jars and lids in boiling water or in a dishwasher on the hottest setting. Make sure everything is chopped and ready to go before you put the salsa on the stove.
Cook. Put all of your ingredients into a large stock pan and simmer for at least 30 minutes until the mixture thickens slightly, After simmering, do a taste test. If you prefer your salsa with a little more kick, consider adding an extra pinch of ground cumin or a few more finely chopped jalapenos. If it's too spicy, add a touch more sugar to balance the heat. As long as you do not reduce the sugar, the vinegar, or add more tomatoes, you are fine.
Fill jars. Using a funnel, carefully ladle the hot salsa into the prepared jars, leaving about a ½-inch headspace from the top. This space allows the salsa to expand during processing. Using a clean, damp cloth or paper towel, wipe the rims of the jars to ensure they're free from any residue. Place the sterilized lids on the jars and screw on the bands until they are fingertip-tight.
Process. Prepare a boiling water bath in a large canning pot. The water should be deep enough to cover the jars by at least an inch. Gently lower the filled jars into the boiling water using a jar lifter or a similar tool. Once all the jars are in the pot, put the lid on and let them process for 20 minutes.
Cool and check seals. Carefully remove the jars from the pot using the jar lifter and place them on a wooden board or a thick towel to cool. It's important to let them cool in a draft-free spot. As they cool, you'll likely hear a "pop" or "ping" sound - this is a sign that the jars are sealing. Once cooled, check the seals by pressing down on the center of each lid. If it doesn't pop back, it's sealed. If any jars haven't sealed, refrigerate them and consume within a week.
Store. Store the sealed jars in a cool, dark place. Ideally, wait at least a week before opening to let the flavors meld, but if you can't resist, go ahead and enjoy! The salsa should be consumed within a year for the best quality.