Add chopped chicken then sprinkle with red pepper flakes and season with salt. Cook on medium heat until the chicken is cooked through and no longer pink, about 5 minutes.
Add cherry tomatoes, chopped fresh basil leaves and chopped garlic to the skillet with chicken.
Cook on medium heat for about 3- 5 minutes until the tomatoes release some of their juices. Add spinach and cook until spinach wilts just a little. Taste, and add more salt, if needed.
Add cooked and drained pasta to the skillet with the chicken and vegetables.
Mix everything well, add more seasonings (salt and pepper), if desired. If the sauce seems dry, add a small amount of pasta cooking water.