Cook the rigatoni pasta to al dente according to the package instructions and then drain and set your pasta aside.
Season your chicken breasts with salt and pepper on both sides. In a large skillet, heat 1 tablespoon of olive oil over medium-high heat and brown the seasoned chicken for about 3-4 minutes per side until they turn golden brown. They do not need to be fully cooked at this stage. Remove the chicken from the skillet and set them aside.
In the same skillet, add another tablespoon of olive oil and then add the diced onions. Cook them until they are soft and translucent. Using a wooden spoon stir in the fresh garlic, red pepper flakes, Italian seasoning, and sun-dried tomatoes. Cook them all for an additional 1-2 minutes.
Pour in the heavy cream, chicken broth, and Parmesan cheese. Combine them all and then return the partially cooked chicken breasts to the skillet, nestling them into the creamy sun-dried tomato sauce.
Simmer the chicken and sauce over medium heat for 10-12 minutes, or until the chicken is fully cooked through and the sauce has thickened slightly.
Before removing the juicy chicken, check the internal temperature of the chicken using a meat thermometer. It should register 165°F (75°C) to ensure it's cooked through. Also, taste the sauce and adjust the seasoning with salt and pepper if necessary.
Remove the chicken from the skillet again, then add the cooked pasta to the creamy sauce. Combine well, then return the chicken back to the skillet. Let your creamy pasta dish rest for 5-6 minutes before serving.
Slice and serve the chicken on top of the saucy rigatoni pasta and enjoy!