"Sweet onions cooked in butter and hard apple cider until tender and flavorful make a sweet and sassy complement to your favorite frank-on-a-bun! Use tongs to serve on hot dogs or other sausages in buns with spicy mustard."
Melt butter in a large skillet over medium heat. Add onions and garlic salt; cook and stir until tender and just starting to brown, 5 to 10 minutes. Add hard cider and black pepper; simmer, covered, until flavors combine, about 10 minutes.
Uncover skillet and cook until cooking liquid evaporates, about 5 minutes. Add sugar as needed.