Combine sweet, juicy watermelon chunks with fresh tomato, onion and a red wine vinaigrette for a salad that is the essence of summer.
Combine watermelon and tomatoes in a large bowl; sprinkle with sugar and salt, tossing to coat. Let stand 15 minutes.
Stir in onion, vinegar, and oil. Cover and chill 2 hours. Serve chilled with lettuce leaves, if desired. Sprinkle with cracked black pepper to taste.