Chili's Cajun Alfredo Pasta

8 ounces penne pasta
2 large boneless skinless chicken breasts
2 tablespoons cajun seasoning, divided (see note)
2 tablespoons butter
2 tablespoons flour
2½ cups milk (I used fat free half and half)
salt and pepper to taste
1 teaspoon garlic powder
? cup shredded parmesan cheese
1 tomato, diced (see note)
cilantro, roughly chopped

Cook penne noodles according to package's instructions. Drain and set aside.
Slice chicken in half horizontally so that you have 4 thin pieces of chicken. Season chicken on both sides using 1 tablespoon of the Cajun seasoning. Cook in a greased pan or skillet over medium heat for 6-8 minutes on each side until cooked through.
In a medium sauce pan melt butter over medium-high heat. Add flour and stir until mixture clumps together. Gradually whisk in milk until lumps dissolve and mixture is smooth. Add salt, pepper, garlic powder, and remaining cajun seasoning. Add cheese and stir until melted and incorporated into the sauce.
Toss sauce with the cooked penne noodles. Slice chicken and place on top of pasta, then sprinkle with chopped tomatoes and cilantro.
NOTES
For homemade cajun seasoning, stir together the following: 1 teaspoon salt, 1 teaspoon garlic powder, 1½ teaspoon paprika, and ½ teaspoon each black pepper, onion salt, cayenne pepper, oregano, and crushed red pepper flakes.