In a small bowl, whisk together the chili powder, cumin, pepper, smoked paprika, garlic powder, onion powder, and dried oregano. Set aside.
Working with one piece of chicken at a time, butterfly each breast by slicing horizontally almost all the way through the chicken so that you can open it like a book. Cover the chicken with a piece of plastic and, using a meat mallet, rolling pin, or heavy skillet, pound out the chicken to a scant 1cm thickness. Set aside and repeat with the remaining chicken breasts.
Place a large cast iron or non-stick skillet over high heat. Season the chicken with half of the tex mex seasoning as well as a bit of salt and pepper. Drizzle the chicken breasts with 1 tablespoon of oil and cook, in batches, if needed, for about 2 minutes per side or until golden brown and the chicken is cooked through. Set aside to rest.
Return the pan to the heat and add in a little oil along with the onion and beans. Season with salt and cook, stirring frequently, until the onion is lightly golden, about 5 minutes. Tear the leaves from the cilantro stems and set aside for serving. Thinly slice the cilantro steams and add to the pan along with the corn and remaining tex mex spice mix and continue to cook for 1 to 2 minutes.
Meanwhile, microwave the rice according to the package directions. Add the rice to the pan with the corn and beans and stir to combine.
Slice the chicken and serve alongside the rice with salsa, sour cream, and avocado. Scatter with the cilantro and serve with a chunk of lime on the side.