Be sure to rinse the quinoa well - rinsing the quinoa removes the outer coating that can have a soapy taste. My favorite salsa to use for this is Trader Joe's Tomatillo & Roasted Yellow Chili Salsa. Any salsa will work though! I think kidney beans go so well with with flavors, but you could also use black or pinto beans if you like.
Season the chicken with salt and pepper. Heat 2 tablespoons oil in a large 12-inch skillet (that has a lid for later) over medium heat until hot and rippling. Add the chicken in an even layer. Cook on one side for 3-4 minutes until brown. Then stir and cook for another minute or so on the other side. You aren't looking to cook the chicken all the way through here, just giving it a little color.
Remove the chicken from the skillet onto a plate and set aside. Add another tablespoon of oil to the skillet if needed, then add the onion. Cook for 5-6 minutes until softened. Add the garlic, tomato paste, cumin, chili powder, salt and pepper. Cook for 1-2 minutes until fragrant.
Add the corn, kidney beans, and quinoa. Stir in the salsa, chicken stock, and add the chicken back to the pan. Stir to combine everything evenly then bring to a boil.
Reduce the heat to low, cover, and cook for 20-25 minutes, until the quinoa is cooked through.Top with grated cheddar cheese if desired. Serve with tortilla chips. Enjoy!