One medium red onion, thinly sliced in “rings”
- 2 tablespoons balsamic vinegar
- 1 additional tbsp. olive oil for the balsamic onion
Heat olive oil in a medium saucepan, add the balsamic and then add the onions. Sautee until caramelized and wilted. Serve hot or cold on the burgers. These are super easy and are also great on pizzas and salads.