Place them in a pot with the salt, red chili powder, turmeric, and black pepper.
Add in the water and the curry leaves turn the stove on and bring the soup to a boil.
Wash and rinse the lentils and add them to the pot, cover, and let the mixture simmer.
Use a small wet grinder or blender to make a green-colored paste of the garlic, ginger, and cilantro.
Heat the Ghee and saute the cumin and mustard seeds, in that order, for 30 seconds each.
Add the prepared green paste and saute everything for 1 minute before adding all the ingredients to the tomato mixture.
Cook for 10 minutes, uncover the pot, and use a masher to blend all the ngredients slightly.
Add in the tamarind and cook for an additional 5 minutes.
Let the soup rest covered for 10 minutes before serving.
Video
Notes
Tomatoes - I like Roma tomatoes for their juicy and plump texture. About eight medium-sized tomatoes are 2 cups worth.Curry Leaves - Curry leaves are available at South Asian stores and add delicious taste and aroma to the soup. But if you can't source them, make the soup without them.Ghee - You can swap the Ghee for any other cooking oil you choose, but I highly recommend sticking to it. It gives a delicious nutty taste to the soup and is very easy to source, available at most supermarkets nowadays.Lentils - I like to add the lentils for a little texture, but these aren't essential. Many people make the soup without them, while others add more than two tablespoons to make it thick and hearty. While I like to use Toor Dal (Pigeon Peas), some people use Chana Dal (split chickpeas), masoor dal (red lentils), or moong dal (yellow lentils) instead. So you can experiment a little here, depending on your availability and preference. Soaking the lentils is optional.Tamarind Water - I'm in the habit of taking a block of tamarind and making tamarind water for various recipes. If you don't have any, use one tablespoon of store-bought tamarind paste instead. Since the paste is highly concentrated, one tablespoon is enough!