In a pressure cooker put water, salt, turmeric powder, fresh green chillies, raw mango, tomato and soaked toor dal.
(This recipe also goes well with slightly sauteed split moong dal.)
Mango gives the sourness so you can omit adding tomato. But I like it as it adds colour.

Add few drops of oil. Let everything come to a boil.
Now close the lid of the pressure cooker.

Pressure cook this for 2-3 whistles.
Let the cooker cool down and release pressure.
Open the lid and mix the dal.
I have mashed the mango pulp into the dal and removed the mango seed.

Now for tempering, heat oil.
Splutter mustard seeds, cumin seeds or splutter 1/2 tsp panch phoron, add dry red chillies and a dash of hing. Switch off the heat.
Put fresh curry leaves. Give a mix and put the dal into the tadka.
Cover.
After some time give a gentle mix.
Serve with rice and enjoy!