Slice chicken breast or thighs into thin strips
Slice bell peppers and onion into strips
Mix chicken with oil, lime juice, chili powder, cumin, garlic powder, paprika, salt, and pepper
Marinate for 15 to 30 minutes
Heat a skillet or grill pan over medium-high heat
Cook the chicken until browned and fully cooked
Remove the chicken from the pan
Add the peppers and onion to the same pan
Cook until tender-crisp
Return the chicken to the pan and toss with the vegetables
Warm tortillas
Serve the chicken and vegetables in tortillas with desired toppings