Heat the oil in a large pot over medium heat. Add the onion, carrot and celery and cook until the onion has softened.
Add the garlic and cook for a minute, then add the balsamic vinegar, paprika, cumin, cayenne pepper and lentils and stir to combine.
Add the vegetable stock, salt and pepper to the pot and stir. Half cover the pot with a lid and simmer until the lentils are done (about 10 minutes for the red lentils and 20 minutes for the green or brown lentils).
Stir in the lemon juice and serve with rice or fresh bread, adding the fresh parsley as a garnish.