Ingredients2 Tbsp. vegetable oil
4 to 5 white onions, thinly sliced
2 tsp. kosher salt
²∕³ cup brown sugar
¹∕³ cup apple cider vinegar
• In a large, heavy-bottomed skillet, warm the oil over medium heat. Add the onions and salt and caramelize until light brown, 45 to 60 minutes.
• Add the brown sugar and vinegar and stir until incorporated. Let cool.