Start salted water boiling for the rotini. Once boiling, cook pasta al dente according to package directions, drain, and return to the pot.
Meanwhile, trim the chicken and chop it into bite-sized pieces. Season the chicken with sea salt, pepper, cumin, cayenne, and chili powder.
Heat 1 Tbsp olive oil in a large skillet (use cast iron, if you have it) over medium-high heat until shimmering. Cook chicken over medium-high heat for 7-9 minutes, stirring and flipping occasionally, until cooked through.
While the chicken is cooking, cut up your onion, avocado, and garlic.
Remove the cooked chicken from the pan to a separate bowl. Reduce heat to medium under the skillet, and add 1 tsp olive oil.
Add the onion to the pan and cook over medium heat for four minutes, stirring occasionally and scraping up browned bits from the bottom of the pan. Stir in the garlic and continue to cook briefly over medium heat.
Reduce the heat to low and stir in the sour cream, tomatoes, and avocado for a minute or so to combine.
Pour the avocado/sour cream/tomato mixture over the drained pasta. Squeeze in the lime juice, then toss gently to combine flavors and coat the pasta.
Stir in the reserved cooked chicken, and serve immediately.
Cooking time on the chicken will vary depending on how small you cut it up, so keep an eye on it. You'll get an especially nice sear in a cast iron skillet, but a regular skillet will also work for this recipe.