Boil Pasta: Bring a large pot of salted water to a rolling boil. Cook penne pasta until al dente according to package instructions (about 9 to 10 minutes). Drain, reserving 1/2 cup of pasta water, and set aside.

Season & Sear Chicken: Toss cubed chicken breast with 1 tablespoon Cajun seasoning, salt, and pepper. Heat 1 tablespoon olive oil in a large 12-inch heavy skillet over medium-high heat. Add chicken and sear for 5 to 6 minutes until golden brown and cooked through (internal temp 165°F). Transfer to a warm plate.

Brown Andouille Sausage: Add remaining 1 tablespoon olive oil and sliced andouille sausage to the same skillet. Sear for 4 to 5 minutes, stirring occasionally, until deeply browned with caramelized edges. Transfer sausage to the plate with chicken.

Sauté Aromatics: Reduce skillet heat to medium. Melt 2 tablespoons butter in the savory pan drippings. Add diced yellow onion and red bell pepper. Sauté for 4 to 5 minutes until tender. Add minced garlic and the remaining 1 tablespoon Cajun seasoning; sauté for 60 seconds until fragrant.

Simmer Creamy Cajun Sauce: Pour in fire-roasted tomatoes with their juices, chicken broth, and heavy whipping cream. Stir well, scraping up any flavorful browned bits (fond) stuck to the bottom of the pan. Bring sauce to a gentle simmer for 4 to 5 minutes until slightly thickened. Stir in freshly grated parmesan cheese until completely melted and velvety.

Combine, Garnish & Serve: Return the cooked chicken, andouille sausage, and drained penne pasta to the skillet. Toss thoroughly for 2 minutes to coat every piece of pasta in the rich Cajun cream sauce (add a splash of reserved pasta water if needed to loosen). Remove from heat, garnish with sliced green onions and chopped parsley, and serve piping hot!