Turn on the Instant Pot and set it to Saute mode. Once it's heated, add in oil and cumin seeds.
Once the cumin seeds start to sizzle, add in the chopped garlic and onions. Fry for a few minutes, stirring occasionally, till onions start to brown.
Add in the spices and salt, and give it a quick mix. Add in chopped tomatoes and let it cook for a couple of minutes till the tomatoes start to soften and pulp.
Mix in the lentils and water and let it come to a quick boil. Put on the lid and set the Instant Pot to Manual Pressure Cook mode for 8 minutes, making sure that the valve is in the sealing position.
Let the pressure release naturally before removing the lid.
Add in the chopped spinach and give it a good mix. Serve warm.