In a large pot, bring 4 - 6 quarts of water to a boil. Add salt to taste (about 1 tsp). Add pasta to pot, and stir gently. Return to a boil, and cook pasta until al dente (about 9-11 minutes).
Meanwhile, chop chicken into bite-sized pieces.
In a large skillet, add 2 tbsp butter, chicken, Cajun seasoning, red pepper flakes (if using), and 1 tsp each of salt and pepper. Saute over medium heat until chicken is no longer pink (about 6-8 minutes).
Add remaining 2 tbsp butter, lemon pepper, garlic powder, and heavy cream. Bring mixture to a boil (about 3 minutes), and reduce heat to low.
Before draining pasta, add 1/2 cup of cooking water to Cajun chicken sauce. Drain pasta over a colander in the sink.
Add drained pasta to the Cajun chicken sauce. Remove from the heat and add Parmesan cheese. Allow to rest for 5-10 minutes to allow sauce to thicken.
Portion Cajun chicken pasta on serving plates. Top with tomatoes and additional Parmesan cheese. Serve!