In a large bowl, whisk together chili powder, onion powder, cumin, freshly ground black pepper, and 1 teaspoon kosher salt.
Add the chicken strips to the bowl and toss until evenly coated with the seasoning mixture.
Heat a small amount of olive oil in a large skillet over medium-high heat. Cook the chicken in batches until no longer pink and cooked through, adding more oil as needed to prevent sticking. Transfer cooked chicken to a plate and set aside.
Add additional olive oil to the skillet if needed, then add the sliced onions and bell peppers. Sauté over medium-high heat until tender and slightly charred, about 6–8 minutes.
Return the cooked chicken to the pan with the peppers and onions and stir until everything is heated through and well combined.
Squeeze lime juice over the chicken mixture if desired, then serve immediately with warmed tortillas and optional toppings such as salsa, guacamole, and sour cream.