Rinse the toor dal thoroughly and soak in water for 15 minutes. Drain and add to a pressure cooker with 3 cups of water, turmeric powder, and 1/2 teaspoon salt.

Pressure cook the dal for 4 whistles on medium heat. Once pressure releases naturally, mash the dal lightly with a ladle until smooth and creamy. Set aside.

Heat oil in a heavy-bottomed pan over medium heat. Add mustard seeds and let them splutter. Add cumin seeds, dried red chilies, and curry leaves. Sauté for 30 seconds.

Add minced garlic and sauté until fragrant, about 1 minute. Add chopped onions and green chilies, cook until onions turn golden brown.

Add chopped tomatoes and cook until they break down and become mushy. Add red chili powder and coriander powder, mix well and cook for another minute.

Add the chopped spinach and stir well. Cover and cook until spinach wilts completely, stirring occasionally.

Pour in the cooked dal and mix thoroughly. Add remaining water to achieve desired consistency. Bring to a gentle boil.

Add tamarind paste, jaggery, and remaining salt. Simmer on low heat for 5-7 minutes, allowing flavors to meld together.