1. In a 5 quart saucepan or stockpot, heat olive oil over low heat. Add celery, onion, and carrot, season with salt and pepper and cook until slightly softened and translucent, about 7 minutes.
2. Add spices, stir to combine and cook until fragrant, about 1 minute.
3. Add lentils, tomatoes, 1 tbsp vinegar (reserve 1/2 tbsp for end of cooking) and chicken stock- turn heat to high and bring to a boil. Return heat to low and cover, cook on low until soup is thickened and lentils are fully cooked, 45 minutes to 1 hour.
4. Finish soup with salt and pepper to taste, stir in reserved 1/2 tbsp apple cider vinegar and serve!