How to Make It
Process 6 cups cubed seedless watermelon; 3 cups red heirloom tomatoes, seeded and chopped; 2 Persian cucumbers, peeled and sliced; and 1/4 cup granulated sugar in a blender until very smooth, about 1 minute, stopping to scrape down sides as needed.
Pour mixture through a fine wire-mesh strainer lined with cheesecloth into a large pitcher; discard solids.
Stir in 1/4 cup fresh lime juice; 3/4 to 1 cup tequila or vodka; and, if desired, 1 small jalapeño chile, sliced. Chill until very cold, about 6 hours.
Stir well, and serve over ice. Garnish with cucumber or watermelon wedges and fresh cilantro sprigs.