Preheat the broiler to high. Line a rimmed baking sheet with foil.
Combine the chili powder, 2 teaspoons salt and 1 teaspoon pepper in a small bowl. Put the peppers and onions on the prepared baking sheet, drizzle with 1 tablespoon of the oil and season with half the chili powder mixture. Broil until softened and starting to char, about 10 minutes.
Meanwhile, cut the chicken into 1/4-inch-thick slices and toss in a large bowl with the remaining chile powder mixture and 1 tablespoon oil.
After the peppers are softened and starting to char, about 10 minutes, scatter the chicken on top of the peppers and onions and return the baking sheet to the broiler until the chicken is cooked through and starting to brown, about 5 minutes more. Drizzle with the lime juice.
Serve with the warmed tortillas, Monterey Jack cheese, guacamole, hot sauce, salsa, sour cream and lime wedges.
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