Heat butter in a heavy-bottomed pan and sauté onion until it turns a light golden brown. Add toor dal, masoor dal and rice and stir. Add six and a half cups of water, bring to a boil, lower heat and simmer for fifteen minutes.
Add salt, black pepper powder, coriander leaves and stalks, leek and spinach. Simmer gently for ten minutes. Strain mixture through a sieve and return stock to pan.
Purée the solids and return to the stock. Add pomegranate juice and continue to simmer gently for ten minutes. Adjust seasonings and serve hot.