Blend the buttermilk, mayonnaise, sour cream, cilantro, jalapeno, green onion, minced garlic, lime juice, cumin, oregano, sea salt, and freshly cracked pepper, to taste, using an immersion blender or blender, until well combined and creamy. Set aside in the fridge for 30 minutes to allow the flavors time to mingle.
Place some chopped romaine in a serving bowl, followed by grape tomatoes, diced avocado, green onion, pumpkin seeds, cotija cheese, and tortilla crisps.
Drizzle the salad with the creamy cilantro dressing, then toss to coat evenly.