In a mixing bowl, combine olive oil, lime juice, chili powder, cumin, garlic powder, salt, and black pepper. Add the sliced chicken and mix well to coat. Let it marinate for at least 15 minutes.

Heat a grill or skillet over medium-high heat. Add the marinated chicken and cook for about 5-7 minutes, or until fully cooked and no longer pink.

In the same skillet, add the sliced bell pepper and onion. Cook for about 5 minutes until they are tender and slightly charred.

Serve the cooked chicken and vegetables on warm tortillas. Top with sour cream, shredded cheese, and salsa if desired.