Prepare 7-8 half pint jars or 3 pints, lids, and rings. Sterilize the jars and keep them in the hot water till its time for processing. Make sure to fill your water bath canner and get the water to a simmer.
Remove the stems and de-seed if you want your relish to be less spicy. Clean and peel carrots.
Using a food processor on pulse add jalapenos till they are small diced. Don't just let the machine spin. You want to have pieces not jalapeno juice.
Then add carrots, pulse them the same size, and then finally the red onions. If you don't have a processor you can dice with a knife. Make sure to where gloves when working with the peppers.