Slice the chicken breast into thin, even strips and set aside.
In a small bowl, whisk together the chili powder, smoked paprika, ground cumin, garlic powder, sea salt, and black pepper.
Heat the avocado oil in a large cast-iron skillet over medium-high heat until it begins to shimmer.
Add the chicken strips to the skillet in a single layer and cook for 4-5 minutes until golden brown and cooked through.
Add the sliced red bell pepper, yellow bell pepper, and red onion to the skillet, sautéing for 3-4 minutes until the vegetables are tender-crisp.
Sprinkle the prepared spice blend over the chicken and vegetables, stirring constantly for 1 minute to toast the spices and coat everything evenly.
Remove the skillet from the heat and stir in the fresh lime juice and chopped cilantro.
Top the skillet with sliced avocado and serve immediately while hot.