Red Onion Relish

On hamburgers

Ingredients

1 tablespoon olive oil

1 large red onion, thinly sliced

1 tablespoon red wine vinegar

1 tablespoon minced fresh rosemary

1 1/2 teaspoons sugar

1 1/2 tablespoons mustard

In a large (12-inch) skillet, heat the olive oil over medium heat until shimmering. Add the onion and cook, stirring often, until soft and caramelized, adding water to the pan if necessary to prevent burning. Add the vinegar, rosemary, sugar, and 1 tablespoon of mustard and continue cooking for a few more minutes to blend the flavors. Season to taste with salt and pepper.