How to Make It
Heat light olive oil in a large saucepan over medium. Add onion and garlic, and cook, stirring often, just until tender, about 5 minutes. Stir in turmeric, salt, pepper, nutmeg, and allspice; cook, stirring often, 2 minutes. Add potato and stock, and bring to a simmer. Cook until potato is tender, about 10 minutes.
Reserve a handful of arugula for garnish. Add spinach, cilantro, and remaining arugula to pan. Bring to a simmer over medium, and cook 10 minutes. Working in batches, transfer soup to a blender. Secure lid on blender, and remove center piece of lid to allow steam to escape. Place a clean kitchen towel over opening. Process until smooth. Taste and adjust seasonings if needed, and divide among 4 bowls.
Top each serving with a generous spoonful of Greek yogurt, some of the reserved arugula, and a drizzle of extra-virgin olive oil.