Soak the dal in water for minimum 30 minutes.
Put the dal, tomato, salt, ginger (if used) and water in a heavy-based pan and bring to the boil. Remove the foam then add the turmeric and chili powder. Turn down the heat and gently simmer for 20-25 minutes, or until the dal is cooked, almost creamy.
Heat the oil in a frying pan and stir-fry the cumin and mustard seeds for a minute, or until they start popping. Add the garlic and chili and fry for another minute or so, stirring constantly to make sure they don’t burn. Add the curry leaves, stir for a few seconds, then turn off the heat.Add the asafoetida and garam masala powder, stir for a few seconds.
Add the tadka to the dal and combine.
Serve with a squeeze of lemon juice and garnished with coriander leaves.