Rinse lentils thoroughly under cold water.
Roughly chop your onions and tomatoes. If you don't already have ginger-garlic paste on hand, you can just add in 3-4 cloves of garlic and a small knob of ginger (it all gets blended up at the end).
In a pot, add in your lentils, turmeric, chilli powder, ginger-garlic paste, onions, tomatoes and water. Turn the heat to high. Bring to a boil.
Lower heat to medium. Cover loosely with a lid and let simmer until lentils are soft.
Once the lentils are done, add in your salt and turn off the heat. Check for consistency. If daal is too watery for your liking, cook longer until more water evaporates. If daal is too thick, add water. The 3.5 cups of water in the instructions is just a general guideline - add more or less depending on your taste!
In a small sauce pan, add in your oil and turn the temperature to high. Allow the pan to get nice and hot.
Add in your garlic slices. Wait 30 seconds. Now add in cumin and mustard seeds.
Your mustard seeds should start to pop. Add in your curry leaves, dried chilies, and asafoetida.
Allow spices to cook in the oil for about a minute or so. Once the garlic is brown and the chillies have darkened, take off the heat right away. Be careful not to burn the garlic!
Add your tempered oil to the daal right away and stir. Garnish with cilantro. Your daal is ready to be served!