Heat olive oil in a large deep skillet or Dutch oven over medium-high heat.
Add the sliced smoked sausage and cook for 4-5 minutes until browned. Remove sausage from the skillet and set aside.
In the same skillet, add diced green bell pepper, red bell pepper, and onion. Cook for 4-5 minutes until vegetables are softened.
Add minced garlic, Cajun seasoning, and crushed red pepper flakes to the vegetables. Stir and cook for 1 minute until fragrant.
Return the browned sausage to the skillet and stir to combine.
Pour in the chicken broth and heavy cream, then add the penne pasta. Stir well to combine all ingredients.
Bring the mixture to a boil, then reduce heat to medium-low. Cover and simmer for 15 minutes, stirring occasionally, until the pasta is cooked and most of the liquid is absorbed.
Remove the lid and stir in the shredded cheddar cheese and grated Parmesan cheese until melted and creamy.
Season with salt and freshly ground black pepper to taste.
Garnish with chopped fresh parsley before serving.