Preheat your oven to 425°F. Toss cauliflower florets with 2 tablespoons olive oil, garlic powder, salt, and pepper on a large baking sheet.
Roast for 25-30 minutes, stirring halfway through, until the cauliflower is golden brown and tender. This roasting is what gives the soup its amazing depth of flavor!
While the cauliflower roasts, heat the remaining tablespoon of olive oil in a large pot over medium heat. Add the onion and cook until softened, about 5 minutes.
Add the minced garlic and cook for another minute until fragrant. Stir in the thyme.
Add the roasted cauliflower to the pot along with the vegetable broth. Bring to a simmer and cook for 10 minutes.
Using an immersion blender, puree the soup until completely smooth and creamy. (Alternatively, carefully transfer to a regular blender in batches.)
Stir in the almond milk, nutmeg, and nutritional yeast if using. Season with additional salt and pepper to taste. Garnish with fresh herbs and serve warm. No one will believe there's no cream in this!