Set the Instant Pot in saute mode and add 2 tablespoons of butter.
Once it melts, add onion, ginger, garlic, and green chili. Saute for 3-4 minutes, until the onions soften.
Add tomatoes, turmeric powder, chili powder, and salt. Mix well and saute for 2 minutes.
Add the frozen spinach and 1½ cups of water. Mix well and deglaze the pot.
Cancel the saute mode. Secure the IP lid and set it to pressure cook mode for 5 minutes.
Do a natural release of pressure for 5 minutes, then do a quick release.
Open the IP lid and blend the spinach gravy using an immersion blender.
Set the Instant Pot back to saute mode.
Add the paneer cubes, garam masala, and the remaining 1 tablespoon of butter. Mix well and saute for 2-3 minutes.
Turn off the Instant Pot and add lemon/lime juice.
Serve hot with roti or jeera rice.