To a heated pan, add neutral oil.

Once hot, add mustard seeds and let them splutter. 

To this, add cumin seeds, split black gram lentils, green chilies, ginger, and curry leaves. 

Sauté for 2-3 mins or until the lentils are light brown.  

Add red onions, then cover and cook until they are soft/translucent (5-7mins). 

Add water to the pan if needed to deglaze. 

Add chopped tomatoes along with turmeric, red chili powder, salt, and pepper.

Cover and cook for 15-17 minutes or until they are well cooked, and there is no water in the pan.

Transfer to a blender and blend until smooth and creamy.

Store in a clean, airtight container and keep refrigerated for up to 10 days (or two weeks).