- 1 tablespoon butter
- 1 tablespoon olive oil
- 2 finely chopped red onions (about 3 cups)
- 2 tablespoons balsamic vinegar
In a large skillet, melt butter with olive oil over medium. Add red onions; season. Cook, stirring occasionally, until caramelized, 18 to 20 minutes. Add balsamic vinegar; cook, stirring often, until absorbed, 1 to 2 minutes.