Add in the lentils, water, tomatoes, turmeric and coriander powder, along with some salt into the Instant Pot and give it a mix.
Put on the lid and set the Instant Pot to manual Pressure Cook mode for 4 minutes, making sure that the valve is on the sealing position. Let the pressure release naturally before removing the lid.
Heat oil in a pan and add in cumin seeds.
Once the cumin seeds start to sizzle, add in the garlic and chopped onions. Fry for a few minutes, stirring occasionally, until onions start to brown.
Turn off the heat and add in chili powder giving it a quick mix. Carefully add this into the Dal, making sure to get every last drop of the flavoured oil as well.
Give it a good stir, adjust salt if necessary and garnish with cilantro leaves before serving.