1 Throw the watermelon on a rimmed baking sheet and put it in the freezer for at least 1 hour. 2 When the watermelon is nice and frozen, add it to a blender with the rest of the ingredients. Blend that all up until it is smooth. Taste and add more sweetener if you think it needs it.
Seedless is ideal, but a couple of big seeds aren’t a deal breaker. You could sub .25 cup of this with some tequila if you want to party.