Prep your chicken and veggies. Add the chicken to a large ZipLoc bag along with 2 tablespoons of oil, the ground cumin, chili powder, paprika, garlic powder, cayenne pepper (if using), and some salt & pepper. Let marinate for at least 30 minutes.
Add 1 tablespoon oil to a cast iron skillet or grill pan on medium-high heat. Let the pan get very hot (wait a few minutes). Cook onion and peppers for 7-10 minutes, stirring occasionally, until they're tender-crisp and nicely seared. Take the veggies out of the pan and cover with foil to keep warm.
Add the chicken to the skillet on medium-high heat. Cook the first side for 5 minutes (don't be tempted to move it around the pan - you want a nice sear), and the second side for 3-5 minutes, or until it's cooked through but not overcooked.
Turn the heat off. Take the chicken out of the pan and slice it into strips.
Add the peppers and onions, chicken strips, chopped cilantro, and zucchini noodles to the pan and toss (I like to use tongs). The pan will still be really hot, so the zucchini noodles will warm up a bit without going too watery. Season with more salt & pepper if needed.
Transfer to bowls and top with avocado, Greek yogurt, and lime wedges.