In a bowl, combine sliced chicken with olive oil, chili powder, cumin, garlic powder, onion powder, salt, and pepper. Toss to coat evenly.
Heat a large skillet or cast-iron pan over medium-high heat.
Add the seasoned chicken to the hot skillet in a single layer. Cook for 3-4 minutes per side, until browned and cooked through. Remove chicken from skillet and set aside.
Add the sliced bell pepper and onion to the same skillet. Cook, stirring occasionally, for 5-7 minutes, until softened and slightly charred.
Return the cooked chicken to the skillet with the vegetables. Stir to combine and heat through.
Warm the tortillas according to package directions.
Serve the chicken and vegetable mixture in warm tortillas with your favorite toppings.
Notes
For a better sear, cook chicken and vegetables in batches if your skillet is crowded.
Slice chicken and vegetables uniformly for even cooking.
Consider using a cast-iron skillet for optimal searing and char.