Frozen Watermelon Margaritas

0 Cut up 4 cups of watermelon and spread it out in a single layer on a large cookie sheet or ziplock bag. Freeze at least 2 hours.
3 Prepare rims of margarita glasses by rubbing with a slice of lime then dipping in sugar, salt or tahin.
1 Add all ingredients to a blender and blend until smooth and slushy.
2 Pour into prepared margarita glasses and garnish with a slice of lime.