Mix the fajita seasoning ingredients in a small bowl: chili powder, paprika, salt, onion powder, cumin, garlic powder, sugar, cayenne pepper, and cornstarch. Set the seasoning aside.

Slice the chicken breast into ¼-inch thick strips and coat with two-thirds of the fajita seasoning mixture. Let it sit for a few minutes.

Slice the bell peppers and onion into thin strips. Coat the vegetables with the remaining one-third of the seasoning mix.

Heat 1 tablespoon of canola oil in a skillet over medium-high heat. Add the vegetables and cook for 4 to 5 minutes. Transfer to a plate.

In the same skillet, add the remaining canola oil. Cook the marinated chicken strips for about 4 minutes on each side until browned and fully cooked.

Add the cooked vegetables back to the skillet with the chicken. Mix together for another 2 to 3 minutes until heated through.

Serve chicken and vegetables with warm flour tortillas.

Include optional toppings like pico de gallo, avocado sauce, or crema.