Clean and wash the lentils. Put them to boil. To the boiling lentils, add celery (root). Boil until soft. Add more water if needed.
Add the flour and after it turns golden, add the tomato paste. Mix the resulting mixture with broth from the lentils, until diluted. Pour it into the soup.
Once it comes to a boil again, add whole or chopped garlic cloves. Add a few savory sprigs to the soup and serve.