Prepare a boiling water bath canner and 7-8 half pint jars.

Combine the cherries, lemon juice, calcium water, and 1/2 cup of water in a large pan. Cover and bring to a low boil. Cook, stirring regularly, for 10-12 minutes, until the fruit softens and releases its juice.

Whisk the pectin and lemon zest into the sugar.

When the fruit has softened sufficiently, add the sugar, pectin, and lemon zest mixture. Stir to combine.

Bring the fruit to a boil and cook vigorously for an additional 4-6 minutes, until the jam begins to thicken.

When you've deemed that the jam has thickened sufficiently, remove the pot from the heat.

Funnel jam into prepared jars. Wipe rims, apply lids and rings, and process in a boiling water bath canner for 10 minutes.

When time is up, remove jars from canner and place them on a folded kitchen towel to cool.

When jars are cool enough to handle, remove rings and check seals.

Sealed jars can be stored on the pantry shelf for up to one year. Any unsealed jars should be refrigerated and used promptly.