Combine all of the ingredients for the Cajun Seasoning in a small bowl. Whisk together until well combined and set aside.
Cook the Chicken Breasts
Preheat the oven to 425F and line a sheet pan with parchment paper.
Place the chicken breasts on the lined tray. Pat them dry with paper towel. Drizzle olive oil on the chicken breasts and sprinkle with some of the Cajun Seasoning to cover. Rub in the seasoning and repeat on the other side of the chicken.
Place in the preheated oven for 18-20 minutes or until the internal temperature in the thickest part of the breast reaches a minimum of 165F. When fully cooked, remove from the oven and set aside.
Cook the rest of the dish
Bring a large pot of water to a boil. Salt the water and cook your pasta as per directed on the packaging. Once cooked, drain and set aside.
While the chicken and pasta are cooking, start cooking the vegetables. Place a large skillet or frying pan on medium-high heat.
Drizzle the olive oil in the pan and add the prepared broccoli, onion. When the broccoli starts to become roasted, add the garlic and cook for another couple minutes.
Pour the chicken broth into the hot pan, in order to deglaze the pan and give an extra steam to the veggies. Turn down the heat to low.
Add the Alfredo sauce to the pan with 2 teaspoon of the Cajun Seasoning. Stir so that the spices combine with the sauce. You may add more of the seasoning if you want more flavor and heat.
Bring the sauce to a simmer and then turn off the heat. Add the grated parmesan to the pasta dish and stir to combine.
Once the chicken has baked and rested for a couple minutes, cut it in slices and serve on top of the pasta.