Melt ghee in a soup pot over medium heat.
Add the mustard seeds and cook until they start to pop, about 1 minute.
Add the garlic, ginger and remaining spices. Sauté for 1 minute, or until fragrant.
Stir in the onion, carrot and tomato. Sprinkle with salt and cook until just tender.
Add lentils and stir to coat with the vegetables and spices. Pour in the water or stock and bring to a boil. Lower heat to a simmer and cook until lentils are broken up, about 20 minutes. Taste for seasonings. Serve on its own or with a dollop of yogurt or raita.