Preheat your oven to 425°F (220°C). Spread cauliflower florets on a baking sheet, drizzle with 1 tablespoon olive oil, and season with salt and pepper. Roast for 25 minutes until golden brown, flipping halfway for even caramelization. Roasting adds depth and sweetness to the soup.
While the cauliflower roasts, heat 1 tablespoon olive oil in a large pot over medium heat. Add the diced onion and cook for 4–5 minutes until soft and translucent. Stir in the garlic, curry powder, cumin, and turmeric. Cook for 1 more minute until fragrant—don’t skip this step, as it blooms the spices.
Add the roasted cauliflower to the pot along with the vegetable broth. Stir well to combine and bring the soup to a gentle boil. Once boiling, reduce the heat and let it simmer uncovered for 10–15 minutes to let the flavors meld.
Remove the pot from heat. Use an immersion blender to puree the soup directly in the pot, or carefully transfer it to a countertop blender in batches. Blend until completely smooth and creamy. If you prefer a chunky texture, you can leave some cauliflower pieces intact.
Return the soup to the pot (if using a countertop blender) and stir in the coconut milk. Simmer for another 2–3 minutes, then stir in the lemon juice. Taste and adjust seasoning with more salt, pepper, or lemon juice as needed.
Ladle into bowls and top with chopped fresh cilantro, toasted seeds, or a swirl of coconut milk. Serve warm with crusty bread, naan, or a side salad.