1. Put a heavy-bottomed soup pot over medium-high heat and add 2 tablespoons coconut oil.
2. When oil is hot, add onions and cook, stirring, for about 5 minutes, or until onions are lightly browned.
3. Add ginger, garlic, turmeric, coriander and cayenne and cook for one minute, or just until fragrant.
4. Add carrots, salt and 6 cups water. Raise the heat and bring to a brisk simmer, then put on the lid and turn heat to low.
5. Cook until the carrots are tender, about 15 minutes. Remove from stove and let cool slightly.
6. Purée in a blender in batches, and return to soup pot. Thin with water if necessary; the soup should not be too thick. Set aside.

Meanwhile, make the Tadka

1. Heat remaining tablespoon of coconut oil in a small pan over medium-high heat. When hot, add mustard seeds, cumin seeds and jalapeno pepper.
2. Cook for one minute, or until spices are fragrant and beginning to pop.
3. Pour the spices and oil into the soup along with the chopped cilantro and black pepper.
4. Stir to combine. Taste to adjust salt.

Serving the Soup

1. Reheat soup and serve garnished with cilantro leaves. Give each bowl a generous squeeze of lemon.