Pressure cook moong dal and Grind coconut well in a mixer.
In a a deep pan, add spinach/amaranthus, tomato, garlic, turmeric powder, salt and water and let cook. When it starts boiling, add ground coconut and moong dal. Stir well and let boil for another 3 minutes.
Heat oil in a frying pan. When hot, add mustard seeds and let splutter.Then add cumin, red chilies and onions. Roast well and pour on to the spinach curry.