Turn the Instant Pot to Saute and add in the olive oil and let heat for 1 minute.
Add the onion, celery, carrots and saute for 2-3 minutes, stirring occasionally. Once the onions begin to soften, add in the garlic, oregano, thyme, and tomato paste and saute for 30 seconds to 1 minute. Turn the Instant Pot OFF.
Add in ½ cup of the vegetable broth and vigorously scrape up any browned bits on the bottom of the inner pot.
Add the remaining broth, canned tomatoes, salt, pepper, bay leaf, and crushed red pepper flakes if using.
Place the lid on the inner pot and be sure the vent knob is sealed. Set to cook on HIGH pressure for 10 minutes. To do this, hit manual or pressure cook and use +/- buttons to adjust the time to read 10.
Once the cook time has elapsed, let the pressure release naturally for 15 minutes before doing a quick release of any remaining pressure.
Discard the bay leaf and then using an immersion blender, blend the soup until smooth. Alternatively, transfer the soup to a blender and blend with the lid slightly ajar to allow steam to escape. If using a blender, you will more than likely need to do this in batches.
Add in the balsamic vinegar and if desired, stir in cream and ladle out and serve.
Leftover tomato soup can be stored in the refrigerator for 4-5 days. You can freeze the soup for up to 3 months if made without cream.
If you can find them, use San Marzano tomatoes. The flavor truly is much better than regular canned tomatoes.
Feel free to substitute the whole tomatoes with diced tomatoes.
If using fresh tomatoes, use 10-12 peeled and seeded roma tomatoes.
If you don't have an immersion blender, transfer the soup to a blender and blend with the lid slightly open to allow steam to escape.
Omit the cream for a lighter soup OR for a dairy-free/vegan version.