Wash dal and soak for 3 to 4 hours. Soaking lentils for more hours helps to remove antinutrients from lentils. Drain water completely , rinse with cold water and set aside.
In a pressure pan. Add 1 tablespoon of Oil , mustard seeds, cumin seeds , ginger, garlic , green chillies and onions. Saute till onions turns translucent.
Now add in chopped tomatoes , saute till tomatoes turn mushy . Add chopped spinach , turmeric powder ,mix well everything.
Add soaked dal and 2 cups of water and pressure cook for 1-2 whistles on high heat. When pressure settles on its own , open lid , add salt and keep on simmer for 5 -8 minutes .
Whilst , Heat ghee in a small pan. When the ghee is hot, add mustard seeds, cumin seeds, chopped garlic, curry leaves , dry red chilies and asafoetida. Fry till garlic is slightly browned. Add Kasuri methi / dried fenugreek leaves and red chilli . Switch off the heat.
Immediately pour tempering/ tadak over the cooked dal.
Mix well , simmer for 5 minutes and serve with roti or steamed rice.