In a large soup pot or Dutch oven, sauté the onion in oil over medium heat until translucent.
Add the squash and continue cooking, stirring frequently, until the squash is just fork tender, about 5 minutes.
Deglaze the pan with the white wine and then sprinkle the salt and Emerald City Seasoning over the vegetables. Stir to coat. Turn off the heat and cover the pot, allowing the squash to steam with the seasoning for 2-3 minutes.
Add the vegetable broth to the pot. Working in batches, transfer the soup to a blender and pureé until smooth. Return the soup to the pot and add lemon zest.
Warm gently and serve with additional garnish of Emerald City Seasoning.