In a medium mixing bowl, combine the mayonnaise, sour cream, and buttermilk. Whisk until smooth and well combined.
Add the garlic powder, onion powder, dried parsley, dried dill, salt, and pepper to the mixture. Stir until everything is evenly mixed.
Taste the dressing and adjust the seasoning, adding more salt, pepper, or garlic powder as needed.
For extra flavor, stir in the Parmesan cheese (optional) and mix until smooth. If you'd like a more vibrant herb flavor, you can also add fresh herbs at this stage.
Cover the bowl with plastic wrap or transfer the dressing to an airtight container and refrigerate for at least 30 minutes before serving to let the flavors meld together.
Once chilled, stir the dressing again and serve over salads, as a dip for veggies or breadsticks, or as a topping for sandwiches and wraps.