Cook the penne pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the sliced sausage and cook until browned, about 5-7 minutes.
Add the diced onion and bell peppers to the skillet. Sauté for 3-4 minutes until the vegetables are tender.
Stir in the minced garlic and cook for an additional 1 minute until fragrant.
Pour in the diced tomatoes (with juice), heavy cream, and Cajun seasoning. Stir to combine and bring to a simmer.
Let the mixture simmer for about 5 minutes, allowing it to thicken slightly. Season with salt and pepper to taste.
Add the cooked penne pasta to the skillet and toss to coat the pasta evenly with the sauce.
Remove from heat and stir in the shredded cheddar cheese until melted and creamy.
Serve hot, garnished with sliced green onions.