Sumac Pickled Onions

Peel your red onion and cut in half, lengthwise. Slice onion into thin slivers; place in a medium bowl and, using your hands, toss thoroughly with sumac. Place onions into a clean, glass jar (preferably with a screw-top lid). Pour sugar, red wine vinegar, and water into a small saucepan and bring to a simmer over medium heat, stirring until sugar dissolves. Pour pickling liquid over onions in jar, then seal and refrigerate for at least 3 days.