In a large pot, bring salted water to a rapid boil. Add the spaghetti and cook according to the package directions until al dente. Once cooked, drain the pasta and set aside, reserving a cup of pasta water in case you need to adjust the sauce later.
In a spacious skillet, heat the olive oil over medium-high heat. Once shimmering, add the cubed chicken. Sprinkle the Cajun seasoning, along with a pinch of salt and pepper over the chicken. Cook for about 5-7 minutes until the chicken is well-browned and fully cooked, stirring occasionally. Once done, remove the chicken from the skillet and set it aside on a plate.
In the same skillet (do not clean it out to preserve flavor), add the diced onion and minced garlic, stirring frequently for about 1-2 minutes until the onion becomes translucent. Then, toss in the sliced bell pepper and continue to sauté for another 3-4 minutes until the vegetables are tender and aromatic.
Pour the drained diced tomatoes into the skillet, followed by the chicken broth and heavy cream. Stir to combine. Bring the mixture to a gentle simmer, allowing it to cook for about 5 minutes, which helps the sauce thicken slightly and infuses all flavors together.
Return the sautéed chicken to the skillet and mix well to incorporate. Add the cooked spaghetti into the skillet, tossing until the pasta is evenly coated in the creamy sauce. If the sauce appears too thick, add a splash of the reserved pasta water to achieve your desired consistency.
Off the heat, stir in the grated Parmesan cheese until it melts into the sauce, creating that rich, creamy texture. Taste and adjust the seasoning with additional salt and pepper as needed.
Dish out the creamy Cajun chicken spaghetti onto warm plates. Garnish generously with chopped fresh parsley for a burst of color and flavor.
Notes
Serve with garlic bread and a side salad for a complete meal.