1.Heat oil in a large pot over medium heat. Add garlic and onion, cook for 2 minutes. Add celery and carrot. Cook for 7 - 10 minutes or until softened and the onion is sweet. Add lentils, tomatoes, chicken broth, cumin, coriander, paprika, and bay leaves. Stir.
2.Increase heat and bring to simmer. Scoop scum on the surface off and discard (do this again during cooking if required). Place lid on and turn heat down to medium low. Simmer for 35 - 40 minutes or until lentils are soft. Remove bay leaves.
3.Using a stick blender, do 2 or 3 quick whizzes to thicken the soup. Add a touch of water if you want to adjust soup consistency. Season to taste with salt and pepper.
4.Grate over the zest of the lemon then add a squeeze of lemon juice just before serving. Garnish with parsley and serve with warm crusty bread.