In a large pot, over medium heat, sauté onion until translucent. Add minced garlic and sauté for 30 more seconds.
Add canned pumpkin puree, cauliflower florets, coconut milk, vegetable broth, thyme, salt, and black pepper to the pot. Stir to combine. Cover and bring to a boil.
Turn the heat down to medium low. Keep the soup covered and simmer for 15 minutes, until the cauliflower can be pierced by a fork easily. Turn the heat off.
Use an immersion blender or a regular blender (if it's safe for hot liquids) and blend the soup until it's creamy. If your regular high-speed blender is not safe for hot liquids, wait until the soup cools before blending. Then, you can return the soup to the pot and heat it back up.