Select Saute setting on your Instant Pot and heat 2 tablespoons of the oil and the garlic for 2 minutes, until the garlic is bubbling but not browned. Add the onion, carrots, celery and salt and saute for about 3 minutes, until onion has softened. Add the oregano and pepper and cook for another minute. Add lentils and broth and stir to combine. Add tomato paste in a dollop on top but don’t stir it in.
Secure the lid and set the pressure release to sealing. Press the cancel button to reset the cooking process, then select the Pressure cook or Manual setting adn set the cooking time for 25 minutes at high pressure. The cooker will take about 10 minutes to come up to pressure.
When the cooking program ends, let the pressure release naturally for about 15 minutes, then move the pressure release to Venting to release any extra steam. Open pot and stir the soup to incorporate ingredients.
Ladle the soup into bowls and drizzle with red wine vinegar and sprinkle with parsley. Serve immediately.