To remove pits from the dark sweet cherries used in this recipe, try a cherry pitter (available from cookware shops or catalogs). Otherwise, halve the cherries, then pry the pits out with the tip of a knife.
Stem, pit, and chop cherries. Measure 4 cups chopped cherries.
In a 6- or 8-quart heavy pot combine the 4 cups cherries, pectin, lemon peel, and lemon juice. Bring to boiling, stirring constantly. Add sugar, stirring to combine. Bring mixture to a full rolling boil, stirring constantly. Boil hard for 1 minute, stirring constantly. Remove from heat. Quickly skim off foam with a metal spoon.
Ladle hot jam into hot, sterilized half-pint canning jars, leaving a 1/4-inch headspace. Wipe jar rims; adjust lids.
Process filled jars in a boiling-water canner for 5 minutes (start timing when water returns to boiling). Remove jars from canner; cool on wire racks.