Wash dal and pressure cook it along with tomatoes, few drops of oil and ¾ cups of water for 4 whistles or until dal is soft.
Once pressure releases naturally, add water onions, zucchini and boil until zucchini is cooked.
In a separate pan, heat oil, add mustard, cumin, curry leaves and red chilies. Let the seeds splutter and chilies change color.
Add crushed garlic and fry until light golden brown.
Add chili powder, turmeric and give a quick stir.
Pour the tempering over dal, keeping aside a spoonful for garnish. Cover and let the dal simmer for few minutes. Give a good stir, simmer for few minutes if the dal is too thin.
Turn off the heat, transfer to a serving bowl and garnish with cilantro and remaining tempering.
Green Chilies - If you like green chilies in dal as we do, use 2-3 small green chilies instead of red chilies and chili powder. Add slit chilies to tempering or pressure cook moong dal with green chilies.
Lime Juice - Substitute tomato with 1 tablespoon of lime juice. If using lime juice, add it just before pouring tadka over dal. You can use both tomatoes and lime juice, in which case use less lime juice and adjust it to your liking.
Dal Substitute - Masoor dal is a good substitute for moong dal. Toor dal and chana dal also work but cooking time for these two dals is longer. Pressure cook for 6 -7 whistles.
Zucchini Substitute - Cucumber and tender ridge gourd are a good substitutes. Bottle gourd is also a good substitute and if using bottle gourd, pressure cook the gourd along with moong dal.