Set the Instant Pot to simmer and on medium-high heat. Add the onions and only 2 tablespoons of water. Cook for about 6 minutes while stirring often. We are cooking without oil and that means you'll have to look after your food. Add some more water until the onions are translucent.
Add the tomato fritto and stir. Add the tomato cubes, the sundried tomatoes, the crushed bananas, the bouillon, the salt and the black pepper.
Fill each can of the tomato cubes 2 times with water. In total we add 4 cans of water.
Close the lid on the instapot and close the venting valve. Set to pressure cook for 7 minutes. It will take at least 10 minutes before your pot comes to pressure. After the 10 minutes, let the pressure release for at least 8 minutes before moving the valve to 'vent'.
Mix the soup with an immersion blender. You can also pour the soup in your countertop blender. Just be careful to not overload and keep the top open so the steam can release while mixing.
Did you use fresh tomatoes? Then pour your soup through a sift to make sure there are no skins in your soup.
Season to taste with more pepper and salt.