In a high-speed blender add plums, ½ cup sugar, and honey. Taste and add additional sugar (or honey) if desired.
Let sit for about 25 minutes to macerate before proceeding.
Add lemon juice blend until smooth.
If you have an ice cream maker, follow the manufacturer's directions. Otherwise keep reading.
Transfer the mixture to a freezer safe container and place in freezer for 2-3 hours before serving, stirring every 30 minutes. The stirring is necessary to prevent it from becoming one large fruity ice cube.
Serve when it reaches your desired balance of frozenness and scoop-ability. If it gets too hard, place it on the counter to soften slightly then put in the blender or food processor a little at a time to blend it.