Preheat the oven to 450°F. Smash the garlic cloves with the side of the knife.
Place the cauliflower florets and smashed garlic in a large bowl and drizzle with vegetable broth. Shake the bowl a few times to coat the cauliflower evenly with the broth.
In a small bowl combine the turmeric, cumin, salt and crushed red pepper flakes. Sprinkle evenly over cauliflower, tossing well to coat evenly.
Place the cauliflower on a large rimmed baking sheet and bake in the center of the oven until browned and tender, about 25-30 minutes, turning the florets occasionally so they are evenly cooked. Reserve 1 cup.
Meanwhile, heat a medium pot over medium heat, add some broth and onion and cook until translucent, about 2 to 3 minutes.
Add the broth and transfer the remaining roasted cauliflower to the pot, bring to a boil and cook covered on low 15 minutes.
Use a hand blender (or regular blender carefully in batches) and blend until smooth.
Salt to taste as needed and serve topped with roasted cauliflower and cilantro. You could even drizzle a little Greek yogurt on top, if you’d like. Makes 4 1/2 cups.