- Preheat an oven to 400°F. Line a baking sheet with parchment paper.
- In a bowl, stir together the pumpkin and olive oil, and season with salt and pepper. Spread the pumpkin on the prepared baking sheet and roast until soft and caramelized, 30 to 35 minutes.
- In a large, heavy pot over medium-high heat, melt the butter. Add the onion and garlic and sauté until translucent, about 5 minutes. Add the cumin and coriander and cook for 1 minute. Add the broth and pumpkin and bring to a boil. Reduce the heat to low and simmer for 25 minutes. Remove from the heat and let cool slightly.
- Working in batches, puree the soup in a blender or food processor. Return the soup to the pot and season with salt and pepper.
- Meanwhile, make the spicy pumpkin seeds: Reduce the oven temperature to 350°F. Line a baking sheet with parchment paper.
- In a bowl, stir together the pumpkin seeds and canola oil. In another bowl, stir together the salt, cayenne, cumin and cinnamon. Add the pumpkin seeds to the spice mixture and stir to coat. Spread the seeds in a single layer on the prepared baking sheet and bake, stirring once, until golden brown, 10 to 12 minutes.
- Ladle the soup into warmed bowls, garnish with the pumpkin seeds and serve immediately.