Blend together the water, blackberries, and cashew butter until smooth except for the seeds - they may still be there, but we'll strain them out in the next step.
Pour the mixture through a fine-mesh strainer to remove the seeds, and rinse the blender to remove any leftover seeds or pulp.
Then put the strained mixture back in the clean blender with the sweetener you picked lemon juice, zest, and vanilla.
Pour the mixture in a Ninja Creami pint and freeze for 24 hours. Spin on the ice cream setting.
If it’s still powdery use the respin button.
