Sweet Onion Relish

This tangy-sweet dressing is perfectly paired with tenderloins marinated in whiskey, or served as an appetizer on top of toasted baguette slices. You can prepare the dressing a day or two ahead and put it in the refrigerator; bring it to room temperature before serving. Prepare one or two extra servings for a festive treat.
Melt the butter in a large skillet over medium-high heat. Add the onion to the skillet; cook for 15 minutes or until golden brown, stirring occasionally. Add the vinegar and other ingredients; simmer for 15 minutes or until the liquid has evaporated.