Bring a large stock pot to a roaring boil. Add 2 teaspoons of kosher salt. Add the fettuccine and cook according to package instructions. Drain and set aside.
While the pasta is cooking, slice the chicken in half width wise to make chicken cutlets, or thin looking chicken breasts. You can see this in the video below. Season the chicken on both sides with 2 tablespoons Cajun seasoning.
Heat the extra virgin olive oil in a large skillet over medium heat. Add the seasoned chicken to the skillet. Cook for about four minutes on each side or until the chicken reaches an internal temperature of 165 degrees. Set the chicken aside, tented.
While the chicken is cooking, in a medium sauce pan, melt the butter. Once melted, add the heavy cream. Bring to a simmer, and cook for 15 minutes. The sauce should reduce and thicken.
Stir in the Parmesan cheese and allow it to melt completely. Add the remaining 1 tablespoon Cajun Seasoning and season with salt and pepper to taste.
Toss the cooked fettuccine with the sauce. Slice the chicken and top the pasta with the chicken, parmesan, parsley, and diced tomatoes.