Rinse the toor dal under cold running water two to three times until the water runs clear.

Bring 4 cups of water to a rolling boil in a large pot over high heat.

Add the rinsed dal, minced garlic, minced ginger, slit green chili, turmeric powder, and asafetida; stir to combine.

Reduce heat to medium-low and simmer uncovered for 25 to 30 minutes, stirring occasionally, until the dal is soft and creamy.

Stir in the chopped tomato and salt; simmer for another 5 to 10 minutes until the tomato softens and the dal reaches desired thickness.

If using coconut milk, stir it in and heat through for 2 to 3 minutes without boiling.

While the dal finishes, heat ghee or oil in a small skillet over medium-high heat until it shimmers, about 1 minute.

Add cumin seeds and mustard seeds to the hot oil; let them crackle for about 5 seconds.

Add broken dry red chilies and curry leaves; fry for 5 to 10 seconds until fragrant.

Carefully pour the tempering over the cooked dal and stir well to combine.

Serve hot with rice or flatbread.