How to Make It
Preheat oven to 425°F. Pulse chiles, lime juice, garlic, cumin, and 1 cup of the cilantro in a food processor until mostly smooth.
Season steak with salt. Heat oil in a large cast-iron skillet over high. Cook steak, turning once, until deeply browned, 1½ to 2 minutes per side for medium-rare. Transfer to a cutting board and let rest for 5 minutes; roughly chop.
Layer chips, chile mixture, cheeses, and onion on a rimmed baking sheet (line with foil for easy cleanup). Bake until cheese is melted, 7 to 8 minutes. Top with steak, lime wedges, remaining ¼ cup cilantro, and radishes.