Heat a large skillet or braiser over medium heat. Add the sliced beef sausage and cook for about 4 minutes until lightly browned and slightly crisp. Remove from the skillet and set aside, leaving the flavorful oil in the pan.
Add the mushrooms, red bell pepper, yellow bell pepper, and garlic to the same skillet. Sauté for about 3 minutes until the mushrooms start to brown.
Add the penne pasta, fire-roasted tomatoes, chicken broth, and Cajun seasoning. Stir until everything is evenly combined.
Cover the skillet and bring the mixture to a boil.
Once boiling, reduce the heat to medium and simmer for 12–15 minutes, stirring occasionally, until the pasta is cooked al dente.
Add the cream cheese in small chunks and stir until it fully melts into the sauce.
Return the sausage to the skillet and mix well. Taste and add salt if needed.
Finish the dish by sprinkling fresh parsley and red pepper flakes on top before serving. This final step makes the one pot creamy Cajun sausage pasta even more flavorful.