Step 1

In a 4-quart soup pot over medium heat, heat the oil until shimmering. Add the onion and cook, stirring occasionally, until tender but not brown, 4 to 5 minutes. Add the garlic and ginger and cook, stirring, until aromatic, 30 seconds more. Stir in the cumin, turmeric and cayenne pepper until aromatic, about 30 seconds. Stir in the tomato paste to incorporate, followed by the lentils. Add the broth and salt, and bring to a boil.

Step 2

Reduce the heat to medium-low and simmer, uncovered, for 15 minutes. If the lentils have absorbed most of the broth, add more as needed – start with 1 cup – for a thick but soupy consistency. Add the cauliflower and return the mixture to a boil. Reduce the heat so the soup is at a simmer and cook until the cauliflower is soft, 20 to 25 minutes more. Remove from the heat and, using an immersion blender, puree until smooth. (Or, you can puree the soup in batches in a blender: To prevent spatters, be careful to not fill it more than halfway, remove the center ring from the lid, and hold a kitchen towel over the lid as you blend.) Stir in the coconut milk and lemon juice, then taste, and season with additional salt, if desired.

Step 3

Ladle the soup among the bowls, garnish with a drizzle of coconut milk, if desired, and serve hot.