Cook pasta according to package directions. Drain and set aside.

Pat the steak dry and season generously with Cajun seasoning. Heat olive oil and butter in a large skillet over medium-high heat. Add the steak and cook for 3-4 minutes per side for medium-rare. Remove from skillet and let it rest on a cutting board.

In the same skillet, reduce heat to medium. Add diced onion and bell pepper and sauté for 5-7 minutes until softened. Add minced garlic and cook for 1 more minute until fragrant.

Pour in the chicken broth to deglaze the pan, scraping up any browned bits. Simmer for 2 minutes. Stir in the heavy cream and bring to a gentle simmer, cooking for 3-4 minutes until slightly thickened. Reduce heat to low and stir in the Parmesan cheese until smooth.

Slice the rested steak against the grain into thin strips. Add the cooked pasta and sliced steak to the skillet with the sauce. Toss to combine until everything is coated. Garnish with fresh parsley and serve immediately.