In a medium bowl, combine the watermelon cubes, diced tomato, and sweet onion. In a separate small bowl, whisk together the Balsamic Vinegar, Olive oil & sugar until the sugar has dissolved. Slowly pour the dressing over the salad, using as much or as little as you’d like – I used about 2/3 of the dressing and gently toss. Season with salt and pepper to taste. Cover and refrigerate for a minimum of 30 minutes prior to serving, but the longer you can let it sit & let the flavors meld, the better the salad tastes – I would recommend at least a couple of hours.