Heat the olive oil in a large frying pan over a high heat.
Add the chicken strips and cook for 3 to 4 minutes, stirring often, until lightly browned.
Add the peppers and onion, then sprinkle over the smoked paprika, cumin, garlic powder and chilli flakes, if using. Season with salt and pepper.
Cook for a further 5 to 6 minutes, stirring often, until the chicken is cooked through and the vegetables are just tender.
Squeeze over the lime juice and stir well.
Serve straight away in the warm tortillas, with soured cream, grated cheese and coriander, if you like.