Boil the potatoes for 25 minutes, or until cooked through. Peel the potatoes and pit the olives. In a blender, combine the potatoes, beets, olives, olive oil, apple cider vinegar, garlic, salt, black pepper and cumin. Blend until smooth. Add in the walnuts and blend for a couple of seconds, leaving them chopped into small chunks rather than fully blended. Enjoy!