1. In a large saucepan, heat oil over medium heat. Add onion; cook and stir until softened, 2-3 minutes. Add curry paste; cook until fragrant, 1-2 minutes. Add cauliflower and broth. Increase heat to high; bring to a boil. Reduce heat to medium-low; cook, covered, about 20 minutes.
2. Stir in coconut milk; cook an additional minute. Remove from heat; cool slightly. Puree in batches in a blender or food processor. If desired, top with minced fresh cilantro.