Stirring a couple cups of cold seltzer into this soup right before serving instantly chills it and thins the pureed veggies to a just-right consistency.
In a food processor or blender, in batches, puree 2 pounds roughly chopped tomatoes, 1 peeled and chopped English cucumber, 1 seeded and chopped jalapeño, 1 cup chopped watermelon, ¼ cup loosely packed fresh cilantro leaves, 1 tablespoon fresh lime juice, 1 tablespoon olive oil, and 2 teaspoons kosher salt until smooth with some chunks. Transfer mixture to a large bowl. Stir in 2 cups cold seltzer. Serves 6.