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 2 tablespoons olive oil. Shake the bowl a few times to coat the cauliflower evenly with the oil.
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 1 teaspoon oil 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, stir in coconut milk and serve topped with roasted cauliflower and cilantro with additional coconut milk for drizzling if desired. Makes 4 1/2 cups.