To prepare Lime Salt, using a mortar and pestle, combine salt and lime zest until the salt takes on a bright green color. Set aside.

To prepare watermelon nectar, cut up watermelon flesh and place in a strainer lined with a clean kitchen towel over a bowl. Gather the corners of the towel and squeeze tightly to extract watermelon nectar. Measure 8 ounces; reserve remaining nectar for another use. Combine watermelon nectar, tequila, Simple Syrup, and lime juice in a cocktail shaker. Shake and pour drink through a strainer over ice in glasses. Garnish with lime wedges and Lime Salt.

Combine 1 part water and 1 part sugar in a saucepan. Bring to boiling over medium heat, stirring until sugar is dissolved (syrup is done when the mixture is clear and the surface is covered in bubbles). Remove from heat; cool in refrigerator until ready to use.