Step 1

Add the onions, water, olive oil, and salt to a large pan or pot and mix together. Turn heat to medium-high and and cook covered for 12-15 minutes or until the onions are soft and most of the water has evaporated.

Step 2

Uncover the pot and turn the heat down to medium. Continue to saute until the onions are deeply caramelized (about 30 more minutes). Pay attention to the onions. Adjust heat and/or add a splash of water to prevent burning.

Step 3

Mix the ingredients and give it a taste. Season with salt and pepper to taste.

Step 4

Preheat the oven to 450f and set the rack to the middle level.

Step 5

Heat a large cast iron or stainless steel pan to medium-high heat.

Step 6

Cut the skirt steak into half or thirds so that it can fit into the pan. Pat the steak dry with paper towels and season liberally with salt and pepper on both sides.

Step 7

Add the oil to the pan and once smoking, add the steak. Sear for 3 minutes per side or until well browned. Place the cooked steak on a cutting board and tent with foil for at least 5 minutes. After 5 minutes cut the steak into 4-inch pieces then slice against the grain into 1/4-inch thick slices.

Step 8

Cut the baguette down the middle lengthwise and seperate the two sides. Place the bottom side of the baguette onto a foil lined baking sheet. Spread a layer of the chipotle mayo then layer the steak. Evenly spread the onions on top and then layer the provolone cheese. Place the top side of the baguette onto the baking sheet and spread a thin layer of olive oil so that it will toast.

Step 9

Bake until the cheese melts (about 3-5 minutes). Watch carefully!

Step 10

Spread the chipotle mayo on the top side of baguette. Distribute the optional arugula on top and then close the sandwich. Slice into 4 large or sandwiches. Enjoy!