Take a pan or a wok and heat it.
Add oil and heat it.
Add mustard seeds, slit green chillies and saute well.
Add fresh curry leaves and let them crackle.
Add sliced onions and saute until they turn very slightly golden in color.
Add ginger garlic paste and saute to get rid of raw smell.
Add the chopped tomatoes, add salt as per taste, red chili powder, turmeric powder.
Give a mix and cook well.
Cover the lid and cook until the tomatoes turn soft.
Remove the lid and keep stirring in between.
Add cumin powder and give a mix.
Cook until the tomatoes starts releasing oil from the sides.
When the oil starts to release, switch off the flame.
Garnish with coriander leaves and serve hot with rice or tiffins.