Heat the oven to 400°F (200°C). Cut the pumpkin in half, scoop out the seeds and strings, and cut into large wedges. Brush with 1 tablespoon oil and roast on a baking sheet for 35–45 minutes, until very tender.
When cool enough to handle, scoop the flesh away from the skin. You should have about 4 cups.
Heat the remaining oil in a large pot over medium heat. Cook the onion with a pinch of salt for 6–8 minutes until soft. Add the garlic, ginger, curry powder and cumin and stir for 1 minute.
Add the pumpkin, broth and salt. Bring to a simmer and cook 10 minutes.
Blend until smooth with an immersion blender, or in batches in a countertop blender with the lid vented.
Stir in most of the coconut milk and warm through without boiling. Add the lime juice, then taste and adjust the salt.
Serve with a swirl of the remaining coconut milk, toasted pumpkin seeds and cilantro.
