Bring the mixture to a boil over medium-high heat, stirring occasionally.
Reduce heat and simmer for 10 minutes, stirring frequently.
Ladle hot salsa into hot canning jars, leaving a 1/2-inch headspace.
Remove air bubbles by running a non-metallic utensil around the inside of the jar.
Wipe jar rims clean with a damp cloth.
Center the lid on the jar rim. Screw on the band until fingertip tight.
Place jars in the boiling water bath canner, ensuring they are covered by at least 1 inch of water.
Bring water to a rolling boil, then start the processing time. Process for 15 minutes for pints or 20 minutes for quarts (adjust for altitude if necessary).
Turn off heat, remove canner lid, and let jars sit in the canner for 5 minutes.
Carefully remove jars from the canner and place them on a towel-lined counter to cool completely. Do not retighten bands.
Check seals after 12-24 hours. If a lid does not seal, refrigerate the salsa and consume within a few weeks.
Notes
For best results, use firm, ripe tomatoes. Roma or paste tomatoes work well.
Adjust the amount of jalapeño peppers to your desired level of heat.
Ensure your canning equipment is clean and sterilized to prevent spoilage.
Always follow tested canning guidelines for safety.