In a soup pot, heat the coconut oil on medium heat and add the onion. Cook, stirring occasionally, until the onion is translucent, about 5 minutes. Stir in the ginger, garlic, coriander, turmeric, lentils, and salt, and cook for one minute more.
Add 5 cups water and bring to the boil. Decrease the heat and simmer, stirring occasionally, until the lentils have cooked into a puree, about 20 minutes. Taste and add more salt if needed.
Top each serving with the juice of 1/4 lime and a dollop of yogurt.