Cut the chicken breast into small pieces.
Slice the onion and bell pepper into thin strips.
Heat oil in a pan and stir-fry the chicken breast.
Add the onion and bell pepper to the pan and stir-fry together.
Warm up the tortilla.
Place the sautéed ingredients on top of the tortilla.
Add cheddar cheese, salsa sauce, and lettuce.
Roll up the tortilla tightly.
Slice into bite-sized pieces and serve on a plate.