Fifteen (15) minutes before serving, freeze the feta, a fine grater and a plate (for easier grating)
Combine the watermelon juice, the tequila, the lime juice, and the Cointreau (or triple sec) in a jar and stir well to mix.
Taste and add the sugar if needed. At this step, you can also adjust the tequila or watermelon juice.
Wet the rims of two glasses by dipping them into the plate with the juice.
Fill with the watermelon margarita.
You can strain the watermelon juice or not. Straining will not affect the taste, but it will make your drink brighter red in color.
For a colder drink, make the watermelon margarita and store the jar in the freezer for 30 minutes. I don’t like to use ice cubes because they dilute the taste. If you have the time, you can make watermelon juice ice cubes.