In a large stockpot on medium heat, sauté the onions and garlic with the olive oil, salt, pepper, thyme, and cumin for 5-7 minutes or until the vegetables are translucent and very tender.
Add the celery and carrots and cook for 5-7 more minutes. Add the chicken stock, tomato paste, and lentils. Bring to a boil, reduce the heat and simmer uncovered for 30-45 minutes or until the lentils are cooked and vegetables are fork tender.
Check the seasonings for salt and pepper.
Add the red wine vinegar and serve hot, with a drizzle of olive oil and sprinkled with grated Parmesan.