Preheat the oven to 375. Cut butternut squash in half and scoop out seeds. Place cut-side up on a baking sheet.
Bake for 30-40 minutes, or until tender. Let cool slightly, then scoop out the flesh.
In a large pot, heat olive oil over medium heat. Add onion and cook until softened, about 5 minutes.
Add garlic and ginger and cook for another minute until fragrant.
Add chicken broth and butternut squash flesh to the pot. Bring to a boil, then reduce heat and simmer for 15 minutes.
Use an immersion blender or transfer to a regular blender to blend until smooth.
Season with salt, pepper, and cayenne to taste.