Pre-heat your oven to 375 degrees F (190 degrees C). 

Pour one tablespoon of vegetable or canola oil on top of your turkey breast and rub it around with your hands, rub it all over the breast, making sure not to miss any spots. 

Start sprinkling all of your Cajun seasoning all over the turkey breast. The oil should help all of the seasoning start to stick to the turkey.. Make sure you do not leave any areas of turkey un-seasoned.

Wash your hands.

On a rack in a roasting pan or a rack in a sheet pan, roast your turkey breast for around one to one and a half hours. Preferably you will have a instant read thermometer to watch for over cooking the turkey. 

You are shooting for 165 degrees F (74 C), but you can pull the turkey out around 155 or 160 F and it will carry over five to ten degrees while the meat is resting.

Once the turkey is done, let it sit for an hour and then refrigerate. You can slice it after 10 or 15 minutes of resting time but it will be easier to slice thinly if your turkey is cold.