Set Instant Pot to Saute. Add olive oil and wait 30 seconds to heat up.
Add onion, garlic, carrots, celery, salt, pepper, and saute for 2 minutes.
Add tomato paste, orange slices, bay leaves, cinnamon, red pepper flakes and saute for 1 more minute.
Add lentils, grated tomato, and water. Stir well. Secure cover on Instant Pot.
Set manual time to 22 minutes on Sealing. Once done quick release pressure and serve.