Place the avocado, lime juice, onion powder, garlic powder, buttermilk, parsley, chives and dill in the bowl of a food processor. Add salt and freshly ground black pepper to taste, and process until smooth. Add additional buttermilk to thin the dressing if desired, and adjust the seasoning as necessary and set aside.

Toss the thawed shrimp with 2-3 tablespoons of the blackened seasoning and salt to taste until well coated. Heat the olive oil in a large pan over medium heat, and place the shrimp in the pan in a single layer. Cook on one side for 2-3 minutes until seared, then flip and cook another 2 minutes or until cooked through. Remove from heat and toss with 2 tablespoons fresh lime juice if desired.

Place the shrimp on a serving platter with the avocado ranch dip and additional lime wedges, if desired. Serve immediately and enjoy!