Grind tomato, green chilly and ginger to make a fine paste.
Take some oil in a wok and heat sufficiently. Add asafoetida and cumin seeds when oil is hot. After sauteing cumin seeds, add turmeric powder and coriander powder as well. Stir nicely with a spoon (masala should not burn). Now add tomato paste in the masala and saute until it gets grainy in texture.
Crumble the potatoes and add in this masala and keep stirring for 2 minutes. Add 1 glass water, salt and red chilly powder now (You can increase or decrease the quantity of water as per your preference).
After one simmer, cook for 3 to 4 more minutes. Sabzi is now ready. Add garam masala powder and 1/2 the amount of green coriander.
Aloo-Tomato sabzi is now ready. Take it out in a bowl and garnish with some green coriander. Serve steaming hot aloo-tomato sabzi with poori, paranthas, naan or rice and relish eating.