In a large bowl or baking dish, whisk together all marinade ingredients until well combined. Pound the flank steak with a meat mallet to tenderize, then submerge fully in the marinade. Cover and refrigerate for 24 hours.

Prepare the street corn salad, according to the instructions. Cover and refrigerate. This can be made up to 2 days ahead.

In a small bowl, stir together the sour cream, mayonnaise, chipotle peppers, lime juice, and salt until smooth. Refrigerate until ready to use. Taste and adjust if needed.

Heat a large cast iron skillet over medium-high heat and coat the bottom with avocado oil. Remove the steak from the marinade and let excess drip off. Cook for 5–6 minutes per side, or until the internal temperature reaches about 120°F. Transfer to a cutting board, rest for 5 minutes, then slice thinly against the grain.

Heat a large pan over low heat. Lightly butter one side of each tortilla. Place tortillas buttered side down in the pan, top each with about 1/4 cup shredded cheese, and cook until the cheese begins to melt, about 3 minutes. Fold in half and cook until golden and crisp on both sides.

Carefully open each tortilla and fill with sliced carne asada. Top with street corn, chipotle crema, queso fresco, and a squeeze of fresh lime juice. Serve immediately.