In a blender, blend half of a small seedless watermelon. Strain juice through in a fine mesh strainer into a pitcher so the pulp is left out.

With water or some lime juice, wet the top of 2 low-ball or stemless wine glasses. Turn upside down onto a plate of salt and using your fingers press up against the glass so the salt sticks.

Put half the basil leaves and lime juice in each of the glasses and muddle gently with a pestle or the back of a wooden spoon.

Fill glass with ice, 1-ounce each of tequila, 1.5 teaspoons each of Stevia Simple Syrup, and top with watermelon juice.