1. Remove the rind and cut watermelon into 1/2-inch cubes. Place on parchment paper and freeze for 6 hours.
2. When frozen, place cubes in the bowl fitted with the kneading/crushing blade. Pulse for 1 minute.
3. Scrape down the sides of the bowl. Add powdered sugar and yogurt. Mix on Turbo for 20 seconds. 4 Serve immediately in glasses or place the mixture in the freezer for another 30 minutes to form balls.