In a medium bowl, combine the olive oil, lime juice, garlic powder, cumin, chili powder, salt, and pepper. Add the chicken strips and stir to coat. Cover and refrigerate for at least 2 hours.
Heat a large cast iron skillet over medium-high heat. Add the butter and let it melt. Add the bell peppers and onion and cook for 5 minutes, stirring occasionally.
Add the chicken to the skillet and cook for 8-10 minutes, stirring occasionally, until the chicken is cooked through.
Warm the flour tortillas according to package instructions. Serve the chicken and vegetables in the tortillas with sour cream and guacamole.