1/2 cup sugar
1/2 cup water
3 wide strips orange zest
12 ounces watermelon cubes (about 2 cups)
1/4 cup fresh lime juice
2/3 cup white or silver tequila
1/4 cup Triple Sec
In a small saucepan, bring sugar, water, and orange zest to a boil over high. Reduce to a simmer and cook until sugar dissolves, 3 minutes. Let syrup cool in a bowl.
In a blender, puree watermelon cubes until smooth. Strain through a fine-mesh sieve, pressing on solids, into a pitcher (you should have about 1 cup juice).
Stir in syrup, lime juice, tequila, and Triple Sec. Fill salt-rimmed glasses with ice, then pour margarita mixture over top. Garnish with lime wedges.