05In a large skillet, heat the olive oil over medium-low heat. Add the onions and cook until softened and golden, 12 to 15 minutes. Add the brown sugar, chipotle, adobo sauce, and 1/2 teaspoon salt and cook, stirring, until the sugar dissolves, about 2 minutes.
06Butter the insides of the buns and place up on the baking sheet with the franks. Broil until the cheese melts and the buns are toasted, 3 to 5 minutes.
07Assemble the hot dogs and top with the caramelized onions.