Cook pasta according to package directions in a large pot of salted water. Reserve 1 cup of pasta water before draining.

While pasta cooks, pat steak strips dry and toss with Cajun seasoning. Heat olive oil in a large skillet over medium-high heat. Sear steak for 2-3 minutes per side until browned. Remove from skillet and set aside.

In the same skillet, melt butter over medium heat. Add diced onion and bell pepper and cook until softened, about 4-5 minutes. Add minced garlic and cook for 1 more minute.

Deglaze the pan with chicken broth, scraping up any browned bits. Bring to a simmer. Reduce heat to low and whisk in heavy cream.

Slowly stir in the grated Parmesan cheese until the sauce is smooth. Season with additional Cajun seasoning, salt, and pepper to taste.

Return the cooked steak and drained pasta to the skillet. Stir to combine, ensuring everything is coated in the sauce. If the sauce is too thick, add a splash of reserved pasta water. Serve immediately.