Add the pasta to the salted boiling water and cook according to the package instructions. Usually, rotini pasta cooks in 12-13 minutes.
While pasta is cooking add olive oil and onion to a large skillet. Cook for about 5 minutes, until the onions soften and start to brown.
Add garlic, tomato paste, and chicken and cook for about 7-8 minutes on medium heat, until chicken is almost cooked through.
Now reduce the heat to low and add the cream, Parmesan, dried basil, salt, pepper, and red pepper flakes. Bring the sauce to a gentle simmer. (In the meantime, drain the pasta and reserve some of the pasta water).
Add the cooked pasta to the sauce and stir well, thinning the sauce with reserve pasta water, if needed. Serve immediately.
