Prepare canner, jars and lids.
In a mixing bowl, combine sugar and cocoa powder and set aside.
In a large, stainless steel pot, combine chopped, pitted cherries and lemon juice, then stir in the sugar and cocoa mixture and, stirring constantly, bring to a full rolling boil that can’t be stirred down.
Add the liquid pectin and continue to stir. Boil hard for one minute and then remove from the heat.
Skim off the foam from the top and ladle chocolate cherry sauce into hot, sterilized jars, leaving ¼-inch headspace at the top. Remove air bubbles and adjust headspace if needed, then wipe the jar rim and place lids on and screw bands down.
Process jars in a hot water bath for 10 minutes (adjust time for altitude if over 1,000 feet). Once finished, remove canner lid and wait another 5 minutes before removing jars. Allow to cool on the counter completely and then store in a cool, dark place until ready to use.