1. Wash cherries and remove pits. Place cherries in a large saucepan with 2 tablespoons water. Bring to a boil and then reduce the temperature to low and place a lid on the pot. Cook for 20 minutes or until cherries soften.
2. Puree the fruit with juices in a blender or food processor, in batches. Return to saucepan. Bring to boiling; reduce heat. Simmer, uncovered, for 1 hour or until mixture starts to thicken (you should be able to scrape and see the bottom of the saucepan), stirring occasionally.
3. Stir in 1/2 cup sugar. Add additional sugar, if desired. Add the lemon juice and stir to combine.
4. Remove from heat. Ladle the butter into hot sterilized half-pint canning jars. Wipe jar rims, apply lids and rings, and process in a boiling water canner for 10 minutes. When time is up, remove jars from the canner and let them cool on a folded kitchen towel or wire rack. Store jars in a cool, dry place for up to six months.