How to Make It
Stir together all ingredients in a medium saucepan, and bring mixture to a boil over high, stirring constantly to dissolve sugar. Reduce heat to medium-low, and simmer until watermelon loses color and liquid is very light pink, about 30 minutes. Pour mixture through a fine wire-mesh strainer into a bowl. (Do not press hard on solids to remove any additional liquid.) Discard solids. Pour syrup (about 4 cups) back into saucepan, and bring to a boil over medium-high. Boil until mixture is reduced by about half, 10 to 15 minutes. Remove from heat, and cool completely, about 1 hour. Store in an airtight container in refrigerator up to 1 week.