01 -
In a wide pan, mix onions, olive oil, water, and salt. Cover and cook on medium-high heat for 12-15 minutes until softened. Then, uncover and lower the heat to medium. Keep stirring and cooking for another 30 minutes until they turn deep brown, adding water if they get too dry.
02 -
In a small bowl, stir together sour cream, mayo, chipotle peppers, and adobo sauce. Taste and adjust seasoning with some salt and pepper.
03 -
Cut steak into sections that fit your pan, pat them dry, and season with pepper and salt generously. Heat a pan with oil over medium-high and cook each piece for around 3 minutes on both sides until browned. Cover with foil for 5 minutes to rest, then slice thinly against the grain.
04 -
Set your oven to 450°F. Cut the baguette lengthwise and place it on a baking tray covered in foil. Spread chipotle mayo on the bottom half, layer with steak, onions, and cheese. Brush the top half with olive oil. Bake for 3-5 minutes until cheese melts. Toss on some arugula, close up the bread, and cut into servings.