Cook the pasta according to package instructions in a large pot of salted boiling water until al dente. Drain and set aside.

Heat the olive oil in a large skillet over medium-high heat. Add the sliced smoked sausage and cook until browned on both sides, about 5 minutes. Remove the sausage from the skillet and set aside.

In the same skillet, add the diced onion and bell pepper. Cook until the vegetables are soft, about 5 minutes. Add the minced garlic and cook for an additional minute until fragrant.

Stir in the tomato paste and Cajun seasoning (if using), cooking for a minute to develop the flavor. Pour in the chicken broth and heavy cream, bringing the mixture to a simmer. Let it cook for a few minutes to slightly thicken.

Return the browned sausage to the skillet. Add the cooked pasta and stir to combine, ensuring the pasta and sausage are evenly coated with the sauce.

Reduce the heat to low. Stir in the shredded cheddar cheese and grated Parmesan cheese until melted and the sauce is smooth. Season with salt and pepper to taste.

Once everything is heated through and well combined, remove from the heat. Garnish with chopped fresh parsley or scallions before serving.