Make a paste of tomatoes, green chilies, and ginger. You can put chopped green chilies if you want. Then do not make a paste of it.
Heat the pan or kadhai on the stove.
Add 2 Tbsp ghee or cooking oil and heat it up.
Add cumin seeds (jeera) in it and let them splutter.
After that add the tomatoes, green chilies and ginger paste in it.
Saute it until it becomes soft. You will see it will leave the oil from the sides.
Add 1/2 tbsp sendha namak (rock salt) or according to your taste.
Add 1/2 tbsp black pepper powder.
Add mashed boiled potatoes.
Mix it well
Now add 1 cup water in it. You can reduce or increase the quantity of water according to your choice.
Mix it well. And cover it with the lid.
Cook for 10 minutes on low medium flame.
Garnish it with finely chopped coriander leaves.
Your aloo tamatar ki sabji is ready to serve it.