To your clean Instant Pot insert, combine chopped onion, carrot, celery, garlic, lentil, tomatoes, thyme, Italian seasoning, salt, and pepper. Pour all the broth into the pot and stir until it is thoroughly combined.

Set your Instant Pot to high on the manual setting and set the timer for 18 minutes. Once it is finished, use the quick release on the valve to let the soup vent quickly. Remove the lid and stir in the spinach. Stir until spinach is wilted down.

Top with parmesan and serve!