Boil the penne pasta in salted water until al dente, then drain and set aside.

Toss the thinly sliced beef with the Cajun seasoning until evenly coated.

Heat the olive oil in a large skillet over medium-high heat. Sear the beef strips for 2 to 3 minutes per side, then remove from the pan.

Melt the butter in the same skillet. Add the diced onion, bell peppers, and minced garlic, cooking until softened.

Pour in the beef broth to deglaze the pan, scraping up any browned bits from the bottom.

Stir in the heavy cream and let it simmer for 3 minutes until the liquid reduces slightly.

Whisk in the grated Parmesan cheese until the sauce is completely smooth.

Return the cooked beef and drained penne to the skillet. Toss well to ensure everything is thoroughly coated in the sauce before serving.