Wash and soak the lentils for a minimum of 30 minutes, an hour is preferred
Stovetop: Combine the lentils with the chilli powder, salt, turmeric, onion and 3 cups of water and bring to a boil. Simmer till completely tender - this can take 40 minutes or more depending on your moong daal.
Instant Pot: Combine the lentils with 3 cups of water and the daal base ingredients. Manual / High pressure for 10, naturally release for 10, then release the remaining pressure and open your IP.
You can use an immersion blender to puree the daal or leave as is. Add water to make the daal more thin or crank up the heat to thicken it depending on how you like to eat it.
Adjust seasoning.
Turn the stove off and add the chopped cilantro, green chillies and a squeeze of lemon juice. Give it a good stir.
Heat the oil in a small frying pan and add the sliced onion, garlic, curry leaves, dried red chillies and cumin seeds.
When the onions have turned a beautiful brown then pour the baghaar/tadka/tempering over the boiled lentils and cover.
Serve with rice or roti.
Notes
You can also use a full cup of moong daal here for a classic Moong Daal Flavour