Sprinkle both sides of each chicken breast with the taco seasoning, salt and pepper. Heat the olive oil in a cast iron pan over medium heat. Add the seasoned chicken breasts to the pan and cook about 5 minutes on each side, turning only once (you want both sides to be seared nicely and have a crispy, golden browned crust). Remove chicken from the pan and place on a plate, cover with foil.
To the same pan the chicken was cooked in, add the butter and melt over medium-low heat. Slowly add the heavy cream, whisking to incorporate all the seasonings and browned bits from the chicken. Whisk constantly and cook for about 2 minutes. Add the Parmesan cheese and salsa, stir until combined. Stir in the cooked pasta and carefully mix until pasta is well coated, reduce heat to low and simmer for a few minutes for the pasta to absorb the sauce. Season with salt and pepper, if needed.
Remove chicken from the foil covered plate, slice into strips. Place the sliced chicken on top of the pasta and sprinkle with cilantro and extra Parmesan cheese, if desired. Serve immediately.