Prepare a baking sheet with parchment paper or lightly oil it. Adjust oven rack to lower-middle position and preheat oven to 375 degrees. Split pumpkin in half with a heavy chef’s knife or cleaver. Scoop out the seeds and save to be roasted if you like. Rub pumpkin on all surfaces with oil and season with salt. Place cut-side-down on the baking sheet and place in the oven. Roast until completely tender, flipping halfway through cooking for a total cook time of 1 to 1 1/2 hours. Remove from the oven and let rest until cool enough to handle.
While the pumpkin is roasting make the soup base. Heat the oil in a medium saucepan over medium heat. Add the onions, celery and carrots. Cook for 5 minutes until softened, stirring occasionally to ensure vegetables do not burn.
Add the garlic, ginger salt, pepper and ground spices. Cook for 1-2 minutes, until fragrant. Stir the whole time to ensure spices do not burn.
Add in the lemon juice to deglaze the pot. Stir to make sure none of the spices are sticking to the bottom of the pot.
Stir in the stock, and add the bayleaf. Bring to a boil and reduce to a simmer for 15 minutes.
Using a large spoon, scoop the flesh out of the pumpkin and add it to the pot. Simmer for 15 minutes longer, then remove bay leaves and discard.
Purée soup in a blender in batches or with a hand blender in the pot until completely smooth, Season soup to taste with salt and pepper.
Serve in bowls with garnishes.
Soup can also be cooled down and stored in the refrigerator for up to 1 week or frozen for up to 6 months. Leftovers always taste amazing so I recommend making a large batch at one time to have on hand and freeze.