In a large, deep, heavy-bottomed pot, combine cherries and lemon juice. Stir in pectin until dissolved. Bring to a full boil over high heat, stirring constantly. Add sugar in a steady stream, stirring constantly. Return to a full boil, stirring constantly to dissolve sugar. Boil hard for 1 minute. Remove from heat and skim off any foam. Stir for 5 to 8 minutes to prevent floating fruit.
Ladle into sterilized jars to within 1⁄4 inch of rim; wipe rims. Apply prepared lids and rings; tighten rings just until fingertip-tight. Process jars in a boiling water canner for 10 minutes. Transfer jars to a towel-lined surface and let rest at room temperature until set. Check seals; refrigerate any unsealed jars for up to 3 weeks.
Notes
Makes about five 8-ounce jars. Tip: You can use a food processor to chop cherries; just make sure all of the pits are removed, then pulse a few times, scrape down the sides and pulse again. Do not purée. Recipe suggestion: Use to fill small baked tart shells and add a dollop of whipped cream. Or spread on crêpes and roll up.