Pre-heat your oven to 350 degrees
Cross-hatch the chicken and sprinkle both sides with the cajun seasoning
In a bowl, mix the mayonnaise and ranch seasoning
Add the vegetable oil to an oven-safe dish and place the chicken on top
Smear each chicken breast with the mayo and ranch mixture. Then bake uncovered for 20 - 30 minutes or until the internal temperature of the chicken is 165 degrees