Mix the Base: In a medium mixing bowl, whisk together mayonnaise, sour cream, and buttermilk until smooth.
Add Herbs & Spices: Stir in parsley, chives, dill, garlic powder, onion powder, salt, and pepper.
Adjust Consistency: If you prefer a thinner dressing, add more buttermilk a tablespoon at a time until desired consistency is reached.
Taste & Adjust: Add lemon juice for extra tang if desired, and adjust seasoning to taste.
Chill: For best flavor, cover and refrigerate for at least 30 minutes before serving to allow flavors to meld.