In a bowl, mix olive oil, chili powder, cumin, garlic powder, onion powder, paprika, salt, and black pepper to create a marinade.
Add the chicken breasts to the marinade, ensuring they are fully coated. Let them marinate for at least 10 minutes (or up to 4 hours in the refrigerator for more flavor).
Heat a skillet or grill pan over medium-high heat. Once hot, add the marinated chicken, cooking for about 5-7 minutes on each side, or until the internal temperature reaches 165°F (75°C) and the chicken is cooked through.
Remove the chicken from the pan and let it rest for a few minutes before slicing it into strips.
In the same skillet, add sliced bell pepper and onion. Sauté for about 3-4 minutes until they are tender but still crisp.
Heat the flour tortillas in a tortilla warmer or wrap them in foil and place them in the oven for a few minutes until warm.
To serve, place the sliced chicken on a tortilla, top with sautéed bell peppers and onions, and garnish with fresh cilantro and lime wedges if desired. Roll the tortilla to enclose the filling, and enjoy!