INGREDIENTS 2 tablespoons olive oil 2 large onions, cut into 1/8-inch-thick slices 1/4 teaspoon salt 1/8 teaspoon ground black pepper 1/3 cup canned beef broth 1/2 cup purchased barbecue sauce 1 1/2 tablespoons apple cider vinegar or white vinegar PREPARATION Heat oil in a large skillet over medium-high heat. Add onions, salt, and pepper; cook until onions begin to brown, stirring frequently, about 8 minutes. Add broth, barbecue sauce, and vinegar. Reduce heat to medium; simmer until sauce thickens, stirring occasionally, about 15 minutes. Note: Can be made 1 day ahead. Cover; chill. Rewarm before serving.