Heat the olive oil in a large deep skillet or wide pot over medium heat.
Add the sliced smoked sausage to the pot and cook for 4 to 5 minutes, stirring occasionally, until the sausage is lightly browned on the edges.
Stir in the chopped yellow onion and cook for 3 to 4 minutes, until the onion softens and turns translucent.
Add the minced garlic to the pot and cook for 30 seconds, stirring constantly, until fragrant but not browned.
Sprinkle in the Cajun seasoning, smoked paprika, dried oregano, salt, and black pepper, stirring well to coat the sausage and onions evenly with the spices.
Pour in the chicken broth and canned crushed tomatoes, stirring to combine and scraping up any browned bits from the bottom of the pot.
Add the uncooked penne pasta to the pot and press it down gently so the pasta is mostly submerged in the liquid.
Bring the mixture to a gentle boil over medium-high heat, then reduce the heat to medium-low and cover the pot with a lid.
Simmer for 12 to 14 minutes, lifting the lid to stir every few minutes, until the pasta is tender and most of the liquid has been absorbed.
Reduce the heat to low, then pour in the heavy cream and stir until the sauce looks smooth and creamy.
Sprinkle in the grated Parmesan cheese and stir until the cheese has melted into the sauce and the pasta is evenly coated.
Remove the pot from the heat, taste the pasta, and adjust the seasoning with a little more salt or black pepper if needed.
Sprinkle the chopped fresh parsley over the top, then let the pasta rest for 2 to 3 minutes before serving so the sauce can thicken slightly.