Soak the daal overnight or for at least six hours. The following day, rinse and drain the water.
Add the daal to a pot. Then add the water, fenugreek seeds, turmeric and salt. Cover and bring to a boil. Once it comes to a boil, turn the heat to medium and simmer remove the foam forming on top of the Daal.
Making the Tadka
Finely chop the tomatoes and garlic.
Heat the oil and temper the black mustard seeds, fenugreek seeds, asafoetida and curry leaves in a pan. Be careful not to burn the spices. It takes less than a minute to temper. Make sure you have all the spices ready before you start to temper them.
Add the chopped tomatoes, and chopped garlic and fry for a couple of minutes.
Next, add the chilli powder, coriander powder and a green chilli slit down the middle. Cook over a medium flame until the tomatoes are soft and cooked.
Finishing the Tomato Pappu.
Once the Daal is cooked and soft, sing the back of a ladle, mash some of the daal until you achieve your desired daal consistency.
Add the tadka and mix well. Cook for a further five minutes.
Garnish with coriander leaves if using and serve hot with rice.