Heat oil in a pan, when it gets heated add cumin seeds and mustard seeds in it and cook it until they became brown.
Now add few curry leaves and potatoes in it, cover it for just 10-15 seconds then stir it well again cover it and give nice stir after every half minute.
Cook potatoes 50% in Oil and then add spices.
Now add turmeric powder and mix it nicely then add red chili powder, finely chopped tomatoes and around 2 glass of water in it and cook it for 1-2 minutes.
Now add salt according to taste and cook it again for just 1 minute.
Now turn the heat off and garnish it with few coriander leaves and serve it hot with roti or chapatti or rotla or rice whichever you like.