Place the inner pot into the Instant Pot. Set it to SAUTÉ mode for 10 minutes. Pour in the oil and let it get hot.
Once the oil is hot, add the mustard seeds, bengal gram dal, and curry leaves. Let the mustard seeds splutter.
Then add the sliced onions and sauté it until it turns translucent.
Next, add the garlic and the green chillies. Sauté for a minute or two.
Add the turmeric powder and mix it once. Finally add the tomatoes, salt and water.
Give a quick sauté and cover the Instant Pot with its lid. SEAL and set it to PRESSURE COOK for 10 minutes.
Once the cooking time is done, Quick Release and open the Instant Pot.
Using a potato masher or an Indian Wooden Masher*, mash down the Tomato Bajji untill there aren't any solids that holds it shape.
Serve it hot with dosa or idlis or chapathis!