Beet Greens with Caramelized Onions

1 tblsp olive oil
1/4 lb yellow onion, diced
1/8 tsp fresh thyme
1/8 tsp fresh rosemary
1 garlic clove, minced
1/8 tsp salt
fresh black pepper
1/8c balsamic vinegar
4c beet leaves, washed and chopped

Heat the oil over medium high heat till it stops sizzling.  Add onions and reduce the heat to medium-low.  Cook slowly, stirring occasionally, until golden brown and caramelized, about 30 minutes.  Add the thyme, rosemary, garlic, salt, and pepper, and vinegar stir well to combine.  Cook for 5-15 more minute.  Add beet greens just to wilt.