Cook penne pasta according to directions on the box. Drain pasta and set aside.
Place chicken breasts in a resealable plastic bag and sprinkle in cajun seasoning. Reseal bag and shake thoroughly until chicken is evenly coated.
In a large skillet, saute chicken breasts in 2 Tablespoons of butter, over medium heat, turning occasionally until cooked through.
In a separate skillet, combine half and half, 2 Tablespoons butter, lemon pepper, salt, black pepper and garlic powder over medium heat, stirring occasionally. Remove from heat when cream mixture starts to bubble.
Pour cream sauce over cooked noodles. Slice chicken breasts into strips. Serve pasta on serving plates, top with chicken breast strips, and sprinkle on diced tomatoes and Parmesan cheese.