3 tablespoons butter
2 large red onions, sliced
2 tablespoons sugar
3 tablespoons balsamic vinegar
Heat butter in large skillet over medium heat. Stir in onions and sugar and cook, stirring frequently, until onions are caramelized (thoroughly wilted and deepened in color), about 20 minutes. Deglaze the pan by stirring in vinegar and then cook until the vinegar has been absorbed into the onion mix and the flavors come together, about 7 minutes. Makes a great topping for grilled fish, meat or chicken.
Source: From Asparagus to Zucchini: A Guide to Cooking Farm-Fresh Seasonal Produce by the Madison Area Community Supported Agriculture Coalition