In a bowl, combine the chicken, one tablespoon avocado oil, salt, cumin, coriander, paprika, chili powder, garlic powder, and black pepper. Toss everything to coat.

Preheat a large cast-iron or stainless-steel skillet over medium heat for 5 minutes. Add two tablespoons avocado oil and heat until shimmering. Add the chicken in a single layer and cook, working in batches, if necessary, until golden brown, around 6 minutes. Flip and cook until golden brown and 185F internally, around 6 more minutes. Transfer to a cutting board and set aside.

To the skillet, add the red pepper, green pepper, onion, and jalapeño, if using. Cook, stirring regularly and lifting any brown bits off the bottom of the skillet, until the vegetables have softened slightly, around 4 minutes. Return the chicken to the pan and serve with your choice of tortillas and toppings.