Heat olive oil in a large pot over medium heat. Add the chopped onion and cook until softened, about 5 minutes.
Add the garlic, celery, and carrots. Cook for another 5 minutes, stirring occasionally.
Stir in the chopped tomatoes (or canned tomatoes) and cook for another 5 minutes until they start to break down.
Add the chickpeas, lentils, and spices (ginger, cinnamon, turmeric, cumin, coriander, paprika, black pepper, and salt). Stir well to combine.
Pour in the vegetable broth or water and bring to a boil. Reduce heat and let it simmer for about 30 minutes, or until the chickpeas and lentils are tender.
Add the vermicelli or thin noodles to the pot and cook for an additional 10 minutes, or until the noodles are cooked.
Stir in the tomato paste, cilantro, and parsley. If you prefer a thicker soup, you can mix the flour with a bit of water to form a slurry and add it to the pot. Stir well and cook for a few more minutes until thickened.
Adjust the seasoning if needed and add lemon juice to taste.
Ladle the Harira into bowls and garnish with lemon wedges and additional fresh cilantro or parsley if desired.
Enjoy your meal!