In a mixing bowl, combine chili powder, smoked paprika, onion powder, garlic powder, salt, cumin, and cayenne pepper. Whisk until evenly blended.

Cut the chicken into uniform strips and coat with olive oil and fajita spice mix.

Heat a skillet over medium-high heat and sear the chicken for 2 minutes. Stir and cook until golden brown (6-8 minutes).

In the same skillet, add more olive oil if needed and sauté sliced onions for 2 minutes. Add red bell peppers and another pinch of salt, cover, and cook until tender (5-7 minutes).

Return the chicken to the skillet, mixing gently with the veggies and heat for an additional minute.

Serve the chicken and vegetable mixture with toppings like guacamole, grape tomatoes, and shallots or green onions.