2.

Melt butter in a medium saucepan over high heat. Add in onions and cook, stirring frequently, until bottom of saucepan is glazed in a pale brown fond, about 5 minutes. Add 2 tablespoons water and scrape up fond with wooden spoon. Continue to cook, stirring frequently, until fond has built up again, about 2 minutes longer. Add 2 more tablespoons water and scrape up browned bits. Repeat cooking, adding water, and scraping until onions are completely softened and a deep, dark brown, 20-30 minutes total. Transfer to a small bowl.