Mix the balsamic vinegar and the sugar in a small sauce pan set over medium heat. When the balsamic vinegar starts to boil, reduce the heat to low and allow it to cook until the liquid has thickened and reduced by half. The balsamic mixture should coat the back of a spoon. Allow to cool to room Temperature
Assemble the Salad
Arrange watermelon on a platter. Spread the arugula, tomatoes, onion and feta evenly over the watermelon. Drizzle the balsamic reduction over the salad and serve.
Notes
Notes:It is best to allow everyone to dress their own salad. This way leftovers will stay fresh and crisp when stored.