Prep the seasoning: In a small bowl, mix chili powder, smoked paprika, cumin, garlic powder, onion powder, oregano, salt, pepper, and cayenne.
Season the chicken: Pat chicken dry. Toss with half the seasoning and 1 tablespoon olive oil.
Let sit 10–15 minutes while you slice the veggies.
Cook the chicken: Heat a large skillet over medium-high. Add the chicken in a single layer. Sear 4–5 minutes per side until browned and cooked through.
Transfer to a plate and squeeze on the lime juice.
Sauté the veggies: In the same skillet, add the remaining 1 tablespoon olive oil. Add peppers and onions with the rest of the seasoning. Cook 5–7 minutes, stirring, until tender-crisp with a bit of char.
Optional base: If using cauliflower rice, sauté it in a little oil with a pinch of salt for 3–5 minutes until just tender.
Assemble: Divide greens or cauliflower rice into bowls.
Top with chicken and fajita veggies.
Finish and serve: Add avocado, cheese (if using), a dollop of sour cream, cilantro, and a squeeze of lime. Taste and adjust salt or lime as needed.