Combine: In a medium bowl, whisk together the sour cream, mayonnaise, lime juice, and lime zest.
Season: Stir in the minced garlic, salt, and fresh cilantro if using.
Thin (if needed): If the cream is too thick to drizzle, whisk in a teaspoon of water at a time until you reach your desired consistency.
Chill: Cover and keep in the refrigerator for 15 to 30 minutes before serving to let the flavors blend.