For the Dal: Place toor dal in a large bowl and cover by 2 inches with cool water. Using your hands, vigorously swish toor dal until water turns cloudy, about 30 seconds. Using a fine-mesh strainer, drain toor dal, discarding the cloudy water.

In a medium pot or Dutch oven, combine toor dal, 4 cups (946ml) water, and 1 tablespoon salt, and bring to a boil over high heat. Reduce heat to medium-low and simmer, skimming any foam that collects at the top, until peas are soft and break apart easily when pressed between your fingers, about 45 minutes. Add tomato, onion, and turmeric, stirring to combine. (Toor dal should be covered with water by ½ inch. If the peas look dry and are beginning to stick to bottom of pot, add enough water to cover by ½ an inch.) Simmer until onion and tomato have softened, 10 to 15 minutes.

For the Tadka: In a small saucepan or skillet, heat oil over high heat until it just begins to smoke. Reduce heat to medium, and carefully add asafoetida, mustard seeds, and cumin seeds. Cook, allowing seeds to sizzle and pop, about 10 seconds. Add garlic, coriander, cayenne pepper, curry leaves, and fenugreek leaves and cook, stirring constantly, until curry leaves sizzle, about 10 seconds more. Immediately pour tadka over daal and stir to incorporate. Garnish pot of toor dal with cilantro leaves and 1 tablespoon ghee. Serve with white rice, roti, or as an accompaniment to any Indian meal.