Add olive oil to the Instant Pot. Press the sauté button. Leave the adjustable temperature setting at normal.
When the oil begins to shimmer, add the diced onion, salt, garam masala, red pepper flakes, and cayenne. Use a long-handled wooden spoon or spatula to stir, and continue cooking until the onions have softened and the spices are fragrant.
Add the diced garlic, stir, and continue cooking for 1 minute.
Add the tomatoes, and bring to a simmer.
Add the lentils and water, and bring back to a simmer.
Press the cancel button on your Instant Pot (to turn off the sauté function).
Seal the Instant Pot lid, and turn the steam valve to the sealing position.
Set Instant Pot to pressure cook/manual, high pressure. Set the cook time for 1 minute.
The Instant Pot will take about 10 minutes to come to pressure, and then will start counting down the cook time.The Instant Pot will beep to let you know the cook time has finished. After the cook time is finished, the machine will begin the natural release process, and the countdown timer will start counting up. Allow the Instant Pot to do a natural release for 10 minutes. After 10 minutes, carefully quick release the remaining pressure by using the handle of a long spoon (I use a wooden spoon) to turn the steam valve to venting.Tip: Quick release can be messy– the vent will shoot some liquids out with the steam. Lay a kitchen towel over the top to keep your kitchen clean.
Wait for the steam to escape and the pin to drop down. Then, carefully remove the lid. Stir dal.
Serve Immediately:Serve dal warm, alone or with rice.Leftovers:Store leftovers in the fridge, and use within 3-4 days.Make Ahead and Freeze:Let lentils cool to room temperature, and freeze for up to 6 months