Cook the penne pasta according to package instructions, then drain.
In a large skillet, heat olive oil over medium heat and sauté the onions until translucent.
Add minced garlic and diced bell pepper; sauté for another 2-3 minutes.
Increase the heat and stir in the Cajun sausage, allowing it to brown.
Stir in diced tomatoes and Cajun seasoning; simmer for 5 minutes.
Pour in the heavy cream, stirring thoroughly to combine.
Add the cooked penne pasta to the skillet, mixing well.
Season with salt and pepper; simmer for a few more minutes.
Serve hot, garnished with fresh parsley.