This is actually an abbreviated version of a recipe my hubby Eddie learned in a cooking class. He makes it frequently as a side for meat dishes. The flavors, sugar against balsamic vinegar and red onions, always gets appreciative comments from guests. So, without further adieu, this is the recipe:
1 – 2 red onion, thinly chopped
2 tablespoons olive oil
1 tablespoon butter
1/4 cup balsamic vinegar
1/4 teaspoon red pepper
Heat olive oil and butter in a large skillet over medium heat; stir in onions and cook until translucent, add sugar in the hot oil until onions start to caramelize, up to about 15 minutes. Stir in balsamic vinegar into onion mixture and bring to a boil. Reduce to your preference. Tip: Eddie says you can precook onion and sugar, set aside, then heat up with balsamic just before serving over spinach.