Spread a kitchen towel on the counter. Use your jar lifter to remove warm jars from canner, drain, and line up on the towel.
Use the canning funnel and ladle to fill the jars with tomatillo salsa. Leave 1/2-inch headspace. Run your bubble popper through the jars to release bubbles. Wipe the rims. Use your magnetic lid lifter to lift lids out of the warm water, center lid on the jar, and screw on band until it is fingertip tight.
Place the filled jars back into the canner. Adjust the water level to at least one inch above the jar tops.
Cover and bring to boil over high heat. Once the water boils vigorously, continue boiling for 20 minutes at altitudes of less than 1,000 ft. (adjust processing time for your altitude if necessary).
When the processing time is complete, turn off the heat and let the canner cool and settle for about 5 minutes.
Spread a kitchen towel on the counter. Remove the cover by tilting the lid away from you so that steam does not burn your face. Use a jar lifter to lift the jars from canner and place on the towel.
After 12 to 24-hours, check to be sure jar lids have sealed by pushing on the center of the lid. The lid should not pop up. If the lid flexes up and down, it did not seal. Refrigerate jar and use up within a week.
Remove the screw on bands and wash the jars. Label and date the jars. Store your jars in a cool, dark place and use within 12-18 months. Once the jar is open, refrigerate and use up within a week. Yields 6 pints.