Whisk the base: In a medium bowl, combine mayonnaise and sour cream (or Greek yogurt) until smooth.
Add the spices: Stir in dill, parsley, garlic powder, onion powder, chili powder, cumin, smoked paprika, oregano, salt, and pepper. Whisk until the mixture looks uniform.
Thin to taste: Add buttermilk a little at a time, whisking until you reach your ideal thickness. For a dip, use less; for a pourable dressing, use more.
Brighten it up: Mix in lime juice. Taste and adjust salt, pepper, and heat with a pinch of cayenne or chipotle if you like.
Chill if you can: Transfer to a jar and refrigerate for 20–30 minutes to let the flavors meld. It tastes great right away but even better after resting.
Finish with herbs: Stir in chopped cilantro just before serving for fresh flavor and color.
Thicker: Add an extra spoonful of sour cream or mayo.
Thinner: Whisk in buttermilk or milk, one tablespoon at a time.
Ultra-smooth: Blend for 10 seconds for a silky, restaurant-style texture.
