In a mixing bowl, combine the mayonnaise and buttermilk. Whisk together until well blended and creamy.
Add the ranch dressing mix to the creamy mixture and mix well.
Sprinkle in the black pepper, garlic powder, onion powder, paprika, and cayenne pepper. Whisk until all spices are evenly distributed.
Taste the dressing and adjust the seasoning to your liking.
Transfer to a storage container, seal, and chill in the refrigerator for at least 30 minutes.
Serve the dressing over salads, as a dip, or with any dish that needs a creamy kick.