Heat oil in a non-stick frying pan or skillet over medium heat.

Add pureed onion and tomato, ginger paste, and garlic paste to the hot oil.

Stir and cook for about 2-3 minutes until the raw aroma disappears.

Stir in cumin powder, coriander powder, turmeric powder, and chili powder.

Cook for another minute until the spices are fragrant.

Add chopped mustard greens to the pan.

Mix well with the onion-tomato-spice mixture.

Pour in 1 cup of lukewarm water and stir to combine all the ingredients.

Season with salt according to taste.

Cover the pan and let the mustard greens cook for about 25 minutes on medium-low heat, stirring occasionally, until they are tender.

Once the mustard greens are cooked to your liking, remove the pan from the heat.

Serve hot as a main course, accompanied by rice or Indian flatbread.