Step 1: In a medium-sized mixing bowl, combine the mayonnaise and sour cream. Whisk until the mixture is completely smooth and free of lumps.
Step 2: Slowly pour in the buttermilk while continuing to whisk. Start with 1/4 cup and increase up to 1/2 cup depending on if you want a thicker dip or a thinner dressing.
Step 3: Add the dried dill, parsley, chives, garlic powder, onion powder, salt, and black pepper to the bowl.
Step 4: Stir in the lemon juice or vinegar. This acidity is crucial for balancing the richness of the fats.
Step 5: Taste the dressing and adjust the salt or pepper if necessary. If the herbs feel too subtle, add another pinch of dill.
Step 6: Transfer the mixture to a glass jar and refrigerate for at least 30 minutes. This allows the dry spices to hydrate and the flavors to fully meld.
Step 7: Give the dressing a quick stir before serving. It will keep in the refrigerator for up to 7 days.