Add the chicken, 1 tablespoon of oil, lime juice, chili powder, cumin, garlic powder, smoked paprika, oregano, salt, and pepper to a large bowl. Toss until the chicken is well coated in the spices. Cover and let marinate for 30 minutes and up to 8 hours.
1½ pounds boneless, skinless chicken breasts, 3 tablespoons vegetable oil, 1 lime, 1 tablespoon chili powder, 1 tablespoon ground cumin, 1 teaspoon garlic powder, 1 teaspoon smoked paprika, 1 teaspoon Mexican oregano, 1 teaspoon kosher salt, ½ teaspoon ground black pepper
In a large cast iron skillet, heat 1 tablespoon oil. Add the chicken in a single layer, cooking in batches if needed, and cook, stirring occasionally, until cooked through and golden, about 10 minutes. Set aside.
To the same skillet, add in the remaining oil. One hot, add in the onion and pepper. Cook, stirring often until golden and softened, about 5-10 minutes.
1 yellow onion, 1 red bell pepper, 1 yellow bell pepper, 1 green bell pepper
Add the chicken back to the pan and stir to combine.
Serve hot with tortillas and any desired toppings.
8 flour tortillas, Optional toppings: