Slice the Chicken: Place the chicken breasts on a cutting board and orient them lengthwise. Slice each breast diagonally against the grain into strips approximately 1cm / 0.4in wide and 7.5cm / 3in long. Cutting against the grain shortens the muscle fibers and produces tender strips that stay juicy after high-heat searing rather than turning tough.
Build the Marinade: Combine 2 tablespoons of olive oil, 3 tablespoons of fresh lime juice, smoked paprika, ground cumin, garlic powder, onion powder, chili powder, kosher salt, and black pepper in a medium mixing bowl. Whisk the mixture vigorously for 30 seconds until the oil and citrus are fully emulsified and the spices are evenly distributed with no dry pockets visible at the bottom of the bowl.
Marinate the Chicken: Add the sliced chicken strips to the bowl with the marinade. Toss thoroughly with tongs until every strip is fully coated on all sides. Cover the bowl with plastic wrap and refrigerate for 30 minutes. A 30-minute marination window allows the lime juice to begin denaturing surface proteins for better browning without breaking down the texture of the meat.
Prepare the Vegetables: While the chicken marinates, slice the red bell pepper, green bell pepper, and yellow onion on the cutting board to the specified dimensions. Keep the pepper strips and onion slices in a single pile, as they will cook together in the same pan. Uniform cuts ensure the peppers and onions caramelize at the same rate without some pieces burning while others remain raw.
Sear the Chicken: Heat 1 tablespoon of olive oil in a 12-inch cast iron skillet over high heat for 2 minutes until the oil begins to smoke lightly. Remove the chicken strips from the marinade with tongs, allowing excess marinade to drip off, and arrange them in a single layer in the skillet. Sear for 4 minutes without stirring until the undersides develop a deep brown crust, then flip and cook for 3 minutes until each strip registers an internal temperature of 74°C / 165°F on an instant-read thermometer and the surface is charred at the edges.
Rest the Chicken: Transfer the cooked chicken strips to a clean cutting board and tent loosely with aluminum foil. Rest for 5 minutes. Resting allows the muscle fibers to reabsorb juices that migrated to the surface during cooking, preventing a dry texture when the strips are sliced or served.
Saute the Peppers and Onions: Return the cast iron skillet to high heat without wiping it out. Add the sliced bell peppers and onion directly to the residual fond and oil in the pan. Saute for 7 minutes, stirring every 60 seconds with tongs, until the onion edges turn translucent and develop light char marks and the bell pepper strips are tender with visible browning on the flat cut surfaces.
Warm the Tortillas: Place one flour tortilla in a dry skillet over medium heat for 30 seconds per side until the surface develops small brown spots and the tortilla becomes pliable and steaming hot. Repeat with the remaining 7 tortillas, stacking them under a clean kitchen towel to retain heat until serving.
Assemble and Serve: Arrange the sauteed peppers and onions on a warm serving platter. Layer the rested chicken strips over the vegetables. Serve the warm tortillas alongside the platter and allow each person to fill their own, so the tortillas stay intact and do not become soggy before eating.
