Turn Instant Pot to Sauté setting and pour in olive oil. When oil is hot, put in chicken, sprinkle with Cajun seasoning, salt, and pepper. Cook until it gets browned.
Put in onion, garlic, and bell pepper; sauté until tender and aromatic.
Add chicken broth, then put in pasta and stir to mix.
Secure lid, switch Instant Pot to Manual, and set timer to 4 minutes.
After cooking finishes, do a quick release to allow steam to escape.
Mix in heavy cream and Parmesan cheese until melted and smooth.
Check seasoning and adjust; if you want more heat, add cayenne pepper.
Serve hot, topped with fresh parsley.