Slice 1 1/2 lb chicken breast or thighs into strips and place in a bowl. Add 1 packet of fajita seasoning to the chicken and stir to combine.
In a large cast iron pan, heat 4 Tbsp olive oil over high heat and cook the chicken strips until fully cooked. (About 6-8 minutes)
Remove the chicken from the cast iron and set it aside. Then add in 1/2 sliced onions. Cook the onions until they become translucent.
Add in 1 sliced green bell pepper and 1 sliced red pepper and cook them for about 4 minutes. Be careful not to overcook the peppers. You want them to be tender and crisp. Now, stir in 1 cup of frozen sweet corn (not pictured) this is optional.
Place the cooked chicken back into the pan and cook with the bell peppers and onions for another 2-3 minutes.
Place the chicken and bell peppers into a flour tortilla and serve with sour cream.