Wash the green lentils and chop finely the onion, garlic and fresh coriander.
Add the olive oil to a large pot and fry the onions for 3 to 5 minutes until they are soft. Then, add the garlic and coriander and fry for 30 seconds.
Add the turmeric, ground cumin, paprika and chili flakes and fry for 30 seconds, then add the passata, lentils, and vegetable broth. Add salt and pepper.
Bring to a boil and let it simmer uncovered for 4-5 minutes. Then, reduce to medium heat and cover the pot. Simmer for 40 minutes and check regularly: if the soup is getting dry, add some water.
Once the green lentils get soft, the soup is ready! Serve and garnish with fresh coriander.
Notes
Soak the lentils overnight if you wish to reduce the cooking time.