In a food processor (or blender works too), purée cilantro leaves with the pickled jalapenos and 2 tbsp of their juice. Purée until as minced as possible, scraping down the sides a few times.
Put the mayo and sour cream in a mixing bowl. Add the ranch seasoning, garlic powder, and salt. Mix well to combine.
Pour cilantro mixture directly into the sour cream mixture. Stir to combine. Add lime juice, then a little buttermilk if needed to thin it out, a splash at a time until you reach desired consistency.
Store in a mason jar, condiment bottle, or a bowl tightly sealed. Refrigerate up to five days. Best served chilled so they flavors have time to meld together.