1. Combine first 6 ingredients in a medium saucepan, and bring to a boil. Stir constantly until sugar dissolves.
2. Add onion, and stir to mix. Reduce heat to low, and cook, stirring occasionally, 2 to 3 minutes or until onion turns translucent and pink. Remove from heat, and cool slightly. Chill in an airtight container 2 hours or until ready to serve. Store in refrigerator up to 7 days.