Cook the penne pasta according to package instructions. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the cubed chicken and sprinkle with Cajun seasoning. Cook for 5-6 minutes until browned and cooked through.
Add the diced onion and cook for 3-4 minutes until softened. Stir in the minced garlic and cook for 30 seconds until fragrant.
Pour in the diced tomatoes and heavy cream. Stir to combine and let simmer for 3-4 minutes until the sauce thickens slightly.
Add the cooked pasta to the skillet and toss until well coated in the sauce.
Adjust the seasoning: Start with 2 tablespoons of Cajun seasoning and add more to taste. Some blends can be quite salty or spicy, so adjust based on your preference.
Pasta options: Penne holds the creamy sauce well, but rotini, rigatoni, or even fettuccine are great alternatives.
Tomato variation: Fire-roasted diced tomatoes add a subtle smoky flavor. If using plain diced tomatoes, add a pinch of smoked paprika for depth.
Cream swaps: You can use half-and-half or a mix of milk and butter instead of heavy cream, though the sauce will be lighter and less rich.
Finishing touches: Garnish with freshly grated parmesan, chopped parsley, or a squeeze of lemon juice to brighten the final dish.
Thicker sauce tip: Let the sauce simmer a bit longer before adding the pasta if you prefer a thicker consistency.