Rinse cherries under cool, running water.

Remove and discard the cherry pits and chop the cherries in a bowl.

Place the cherries in a large saucepan or jam pot. Add 1½ cups of sugar and stir to combine.

Over medium-high heat, bring the cherry mixture to a soft boil, stirring often.

Reduce the heat to low and allow the cherry mixture to simmer gently, uncovered, for at least one hour. Stir occasionally, and if the mixture begins to stick to the bottom of the pot, reduce the heat more if possible.

Remove from heat once the mixture has reduced in volume and the color is deep red. 

Puree the cherry mixture in a food processor, food mill, or immersion blender to produce a smooth cherry pulp.

Taste the cherry butter and add the remaining ½ cup of sugar if desired. Add the lemon juice and stir to combine thoroughly.

Check the thickness of your cherry butter by scooping a spoonful of the mixture onto a spoon. If the mixture forms a mound, it is done. If the cherry butter runs off the edges of the spoon, cook the butter longer until it forms a mound on a spoon.  

Ladle or pour the jam into prepared jars or containers. Maintain ¼" headspace if you are going to can your cherry butter. Wipe the rims of the jars or containers with a damp, clean cloth and affix the lids.

If canning, process the jars for 15 minutes (or 20 minutes if above 6,000 feet in elevation).  These times are for both pints and half pints.