01
Place the watermelon cubes into a blender. Blend on high until completely liquefied and pour through a fine-mesh sieve.
02
Pour the salt onto a small plate. Run a lime wedge around the rim of a highball glass. Dip the wet rim into the salt.
03
In a cocktail shaker filled with ice, combine the tequila, watermelon juice, grapefruit juice, lime juice, and agave syrup. Shake well.