Watermelon Key Lime Sorbet

Name: Watermelon Key Lime Sorbet
Ingredients: 3 cups peeled, diced and frozen watermelon, small chunks; 2 key limes, peeled (you can substitute 1 peeled regular lime); 1 tbsp maple syrup (optional) or a squirt of stevia ~ see notes; 1/3 cup water; lime zest, for garnish