Rinse the fresh jalapenos and cilantro. Remove stems from the jalapenos. For a milder sauce, slice the jalapenos open and scrape out the seeds and membranes with a spoon; for more heat, leave them in. Roughly chop the jalapenos and cilantro so they blend more evenly.
1-2 fresh jalapenos, 1/2 cup fresh cilantro leaves
In a blender or food processor, add the mayonnaise, sour cream, and buttermilk. This creates a smooth base for the herbs and peppers.
1 cup mayonnaise, 1/2 cup sour cream, 1/2 cup buttermilk
Add the pickled jalapeno slices along with 1–2 tablespoons of their brine, the fresh jalapenos, cilantro, ranch dressing mix, garlic powder, onion powder, lime juice, salt, and black pepper. If using cream cheese and/or Greek yogurt, add them now as well.
3-4 tablespoons pickled jalapeno slices, 1-2 fresh jalapenos, 1/2 cup fresh cilantro leaves, 1 ounce ranch dressing mix, 1/2 teaspoon garlic powder, 1/4 teaspoon onion powder, 1/2 lime, 1/4 teaspoon kosher salt, freshly ground black pepper, 1-2 tablespoons cream cheese, 1-2 tablespoons plain Greek yogurt
Blend on medium-high speed until the sauce is smooth, creamy, and the cilantro and jalapenos are fully broken down, about 30–60 seconds. Scrape down the sides of the blender as needed. The texture should be pourable and smooth, not chunky.
Taste the sauce. For more heat, add additional pickled jalapeno (and a bit more brine) or fresh jalapeno and blend again. For more tang, add a splash of lime juice or buttermilk. If too thick, blend in 1–2 tablespoons of buttermilk at a time; if too thin, blend in a spoonful of sour cream or cream cheese.
1/2 cup buttermilk, 3-4 tablespoons pickled jalapeno slices, 1-2 fresh jalapenos, 1/2 lime, 1-2 tablespoons cream cheese
Pour the jalapeno ranch into a glass jar or airtight container. Refrigerate for at least 1 hour, preferably 2–3 hours, to allow the flavors to meld and the sauce to thicken slightly.
Stir the sauce before serving. Use as a dip for tortilla chips, veggies, quesadillas, and chicken tenders, or as a dressing for salads, taco bowls, tacos, burritos, and nachos. Serve chilled.