Place the onion, carrot, celery, garlic, lentils, tomatoes, thyme and Italian seasoning, salt, and pepper in the instant pot. Add broth and stir to combine.
Secure the lid and make sure the vent is set to ‘sealing’.
Set instant pot to ‘Manual’, ‘High’ and set for 18 minutes.
Once the 18-minute cycle has finished, CAREFULLY switch the valve to ‘venting’ for quick release. (Recommended: place a folded towel over the valve to prevent steam from burning hands or creating condensation on cabinets)
Once all pressure is released, remove the lid and stir in spinach or kale.
Optional: serve with fresh herbs, lemon wedges, and parmesan.