Put watermelon in a blender. Blend until smooth. (Alternatively, use a potato masher.)
Strain into an 8″x 8″ glass baking dish and place in freezer. (Don’t use a nonstick dish as you may ruin the non-stick finish when you scrape the granita.)
Every 30 minutes or so, for about 3 to 4 hours, scrape the mixture with a fork, making sure to get the solid bits around the edges.
The granita is ready when it is frozen, but still grainy.
Notes
Learn all about Idaho's watermelon season here!Adapted from a recipe by Shelby Kinkaid at the Diabetic Foodie. Photo courtesy of Ms. Kinkaid.