In a large bowl, drizzle boneless, skinless chicken breasts with olive oil. Generously season with Cajun seasoning, garlic powder, onion powder, smoked paprika, salt, and black pepper. Rub the spices into the chicken thoroughly.

Heat a skillet over medium heat and add a splash of olive oil. Add the seasoned chicken and brown it on each side for about 2–3 minutes until golden. Remove from skillet and set aside.

In your slow cooker, lay the browned chicken at the bottom. Layer sliced bell peppers, chopped onion, and minced garlic over the chicken.

Pour the canned diced tomatoes over the layered chicken and vegetables. Add chicken broth, scraping up browned bits left in the skillet.

Cover the slow cooker and set it to cook on low for 4–5 hours or on high for 2–3 hours.

When the cooking time is up, shred the chicken using two forks directly in the slow cooker and stir into the sauce.

Pour heavy cream and grated Parmesan cheese into the slow cooker, stirring until fully melted and combined. Allow to simmer for about 10 minutes.

Cook the penne pasta according to package instructions in a separate pot. Drain and set aside.

Add the cooked penne pasta to the slow cooker and gently toss everything together, then let it warm through for 15-20 minutes.

Dish out into bowls, garnishing with chopped fresh parsley.