Step 1

Preheat oven to broil, with oven rack 7 to 8 inches from heat. Line a large rimmed baking sheet with foil.

Step 2

Stir oil, chile powder, cumin, paprika, garlic powder and salt together in a large bowl; set aside.

Step 3

Cut chicken breasts in half horizontally (to make chicken cutlets), then cut crosswise into strips. Place the chicken in the bowl with the spice mixture and toss to coat. Arrange the chicken in an even layer on 1 side of the prepared baking sheet. Add poblanos and onion to the bowl and toss with any remaining spice mixture; arrange in an even layer on the baking sheet. Place corn on the baking sheet.

Step 4

Broil until the chicken is lightly charred and cooked through, 7 to 8 minutes. Transfer the chicken to a plate and tent with foil to keep warm. Spread the poblanos and onion out on the baking sheet; turn the corn. Broil until the vegetables are charred and tender, about 5 more minutes.

Step 5

Cut the kernels from the corn cob. Toss the corn kernels with the poblanos and onion. Top tortillas with chicken, vegetables, avocado, sour cream and cilantro. Serve with lime wedges, if desired.