In a large pot, bring salted water to a vigorous boil. Add the fettuccine and cook according to the package instructions, usually about 8-10 minutes, until al dente. Once cooked, reserve 1/2 cup of the pasta water for later use, then drain the pasta and transfer it to a large bowl, tossing it lightly to prevent sticking.
In a medium bowl, add the sliced chicken breasts and sprinkle the Cajun seasoning over them. Toss well until each piece of chicken is evenly coated with the seasoning.
Preheat a large skillet over medium-high heat and drizzle in the olive oil. Once hot, add the seasoned chicken to the skillet. Sauté for approximately 5-7 minutes, stirring occasionally, until the chicken is fully cooked through and has a nice golden-brown exterior. Once done, transfer the chicken to a plate and set aside.
In the same skillet, add the diced onion and sliced bell pepper. Sauté for about 3-4 minutes, stirring frequently, until the vegetables begin to soften. Then, add the minced garlic and halved cherry tomatoes. Cook for an additional 2 minutes until the garlic is fragrant and the tomatoes start to soften.
Pour in the heavy cream and stir the mixture to combine it with the sautéed vegetables. Allow the mixture to reach a gentle simmer. Return the cooked chicken to the skillet, then sprinkle in the grated Parmesan cheese. Stir well to ensure everything is evenly combined. Taste and adjust the seasoning with salt and pepper. If the sauce appears too thick, gradually incorporate the reserved pasta water until achieving your desired consistency.
Add the cooked fettuccine to the skillet. Toss everything together diligently to ensure every strand of pasta is luxuriously coated in the creamy sauce.
To serve, spoon the pasta into individual bowls, making a delightful nest of fettuccine topped with the creamy sauce. Finish by garnishing each serving with a generous sprinkle of freshly chopped parsley for a vibrant touch.
Notes
For a lighter version, substitute heavy cream with half-and-half.