Cook your lentils until they're well done but not mushy.
Grind the onions and tomato into a fine paste.
Heat the oil and add the ginger and garlic pastes. Saute and then add the green chillies and the onion tomato paste. Over medium heat sautxe9 till the raw smell of onion disappears. If the paste looks too dry while sautxe9ing, add 2 tbsps of water and continue cooking.
Once the paste is cooked add the turmeric, coriander, cumin and garam masala powders. Sautxe9 a few times, and add the whole masoor/ lentils. If the lentils are too dry add enough water (between half and one cup should do) to ensure the dal is thick in consistency. Using a wooden spoon, lightly mash the lentils so that dal becomes a little thick in consistency. Add the salt, bring to a boil, turn down the heat and cook for about 5 minutes add it.
Whisk the yogurt and add to the dal, stirring continuously. Turn off the heat and mix the dal well to ensure the yogurt is well blended.
Do not turn up the heat or allow the dal to boil once the yogurt has been added or it will split/ curdle spoiling the appearance of the dish.
Garnish with chopped coriander leaves and serve warm with chappathis, parathas or rice.