Step 5
Make the Tangy Caramelized Onions:
Reduce heat to medium. Add tomato paste and cook, stirring, until warmed through, about 30 seconds. Add Worcestershire and vinegar, scraping up brown bits on the bottom of the pan. Stir in butter and brown sugar and continue to cook, adding water by the tablespoonful if skillet starts to dry out until onions are completely softened and caramelized, 15–20 minutes more. Add 1 Tbsp. water and cook, scraping up brown bits until incorporated, about 30 seconds. Let cool.