Rinse the masoor dal under cold water until the water runs clear.
In a saucepan, add 3 cups of water and the rinsed masoor dal.
Bring to a boil over medium-high heat.
Reduce the heat to low and let the lentils simmer until they are tender, stirring occasionally, for about 15-20 minutes.
In another pan, heat oil over medium heat.
Add the sliced onions and fry them for about 5 minutes until they turn golden brown and caramelized, stirring constantly.
Once the lentils are cooked, add the fried onions to the lentils along with turmeric powder and salt.
Add the remaining 3 cups of water to the lentils, and bring the mixture to a boil.
Let it simmer for a few minutes until the flavors are well combined and the dal reaches the desired consistency.
Adjust salt if needed, and then turn off the heat.