Heat a large saucepan or soup pot over medium heat and add the olive oil. Once the oil is hot, add the carrots, celery, and onion and sauté for 5 minutes. Add the garlic and sauté for another 30 seconds, stirring, until fragrant.
Mix together the paprika, salt, and pepper, and sprinkle it over the vegetables. Add the tomato paste. Stir well to coat the vegetables in the spices and paste.
Pour in the vegetable stock and lentils, stir, and bring to a boil. Once boiling, reduce heat to low and cover. Let simmer for 15-20 minutes, until lentils are tender.
Remove from heat and stir in lemon juice. Taste and adjust seasoning as desired. Serve garnished with chopped parsley and lemon wedges on the side.