Place lentils, tomato, water, garlic, ginger and chilli in a large saucepan and bring to a boil.
Reduce heat to a simmer, cover, and cook until lentils are tender and have lost their shape, about 40 minutes (begin checking that there is still water in the pot at 30 minutes and add small batches of water as needed).
Pick out any tomato skins and whisk dal to emulsify it. Keep warm over low heat
Meanwhile, heat ghee in a medium skillet over high heat.
When ghee begins to smoke, add cumin seeds.
When seeds start sputtering, add the garlic, onion and powder and saute over medium heat until most of the onion has turned dark brown, 5-10 minutes.
Add tomato paste, coriander, turmeric, and cayenne.
Pour the onion/spice mixture over the dal.
Add the butter, cilantro, salt, chilli and lemon juice to taste
Simmer for another 5 minutes, serve hot