Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente. Reserve 1/2 cup of the pasta cooking water, then drain the pasta.

While the pasta cooks, pat the chicken dry and season both sides with salt, pepper, and a light dusting of Cajun seasoning.

Heat 1–2 tablespoons of olive oil in a large skillet over medium-high heat. Add the chicken and sauté until browned and cooked through, about 5–7 minutes per side depending on thickness. Transfer the chicken to a plate and rest for a few minutes, then slice or cube.

In the same skillet, add a little more oil if needed. Sauté the chopped onion and sliced bell pepper over medium heat until softened, about 4–6 minutes. Stir in the minced garlic and cook for 30 seconds until fragrant.

Return the chicken to the skillet. Pour in the heavy cream and sprinkle in the tablespoon of Cajun seasoning. Stir to combine and bring to a gentle simmer. Cook 2–3 minutes until the sauce thickens slightly. Taste and adjust seasoning.

Add the drained pasta to the skillet and toss to coat. If the sauce is too thick, add reserved pasta water a tablespoon at a time until you reach the desired consistency. Serve immediately.