Purée watermelon in a food processor, then strain into a small bowl. Pour into a large ice-filled cocktail shaker and add rum, sugar, lime juice, and zest. Cover, shake, and strain into 2 small tumblers. Garnish with watermelon slices.
Servings 0
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.