Chana Dal

Coat bottom of a large pot with oil and place on medium-low heat.
Add sliced onions and cook for 30 minutes; checking every 10 minutes. Cook till onions wilt and turn golden.
Add chopped tomatoes, tomato paste, turmeric, salt and chilli pepper and turn flame to medium-high. Sauté for 2-3 minutes till tomatoes look jammy (i.e., their liquid has reduced).
Add boiling water, lentils and ginger. Reduce heat to low. Stir and cover pot with lid.
Simmer until lentils are tender- test a grain between your thumb and forefinger- about 1½ hour.
Remove and discard the ginger slices.
The proceeding steps are optional; they are for those who want a thicker, soup-like consistency. If you don't want a soup, but a traditional Pakistani-style Chana Dal, once the lentils are tender, loosen them with a little bit of water till the desired consistency is achieved and taste for salt and red chilli pepper. Serve with fresh, chopped coriander on top.
When lentils have cooled, with a teacup or American measuring cup, transfer 1 cup of lentils and process in a blender till smooth and creamy. Loosen with a little bit of water. Pour back into pot. (For those of you who have an immersion blender, you can blend the soup directly in the pot.)
Slowly add boiling water to soup till desired consistency is achieved. Taste for salt and red chilli pepper.
Serve with fresh coriander or your favourite herb; a sprinkle of paprika or sumac (optional); a drizzle of very good olive oil and lemon wedges to add tanginess.