Bring a large pot of salted boiling water to a boil and cook the pasta according to package instructions. Before you drain the pasta, reserve ½ cup of pasta cooking water. Place the drained pasta back in the pot and drizzle it with olive oil to prevent it from sticking.
Season the chicken strips with ½ tablespoon of Cajun seasoning, salt and pepper. Heat the olive oil in a large skillet over medium-high heat and brown the chicken strips on all sides. Reduce the heat to medium and cook them until fully cooked, about 3 more minutes. Transfer to a plate and keep warm.
Using the same skillet, melt the butter and saute the garlic until fragrant, about 30 seconds. Add the diced tomatoes and cook for an additional 2 minutes.
Pour in the half and half and add the parmesan cheese, remaining tablespoon of Cajun seasoning, and chopped parsley. Simmer until thickened. Add salt and pepper if needed.
Return the chicken strips, along with their juices, to the skillet and continue simmering until the chicken is warmed up.
Mix the chicken and sauce into the pot with the cooked pasta and give everything a stir. Add some pasta cooking water if you feel the sauce is too thick. Top with sliced green onions, more parmesan cheese, and fresh parsley.