- Heat the olive oil in a large saucepan over medium heat. Fry the onion for 5 minutes, stirring occasionally, until softened. Add the garlic and continue to cook for 1 to 2 minutes without browning.
- During this time, put the lentils in another pot and cover it with water. Bring to the boil then drain in a colander.
- Add the lentils to the pan with the onion and garlic, then 1 liter of vegetable stock and the herbs. Stir in the tomato paste and tomatoes, then bring to a boil. Reduce the heat to low and simmer for 40 to 45 minutes, adding more stock as needed, until the lentils are tender and the soup is thick. Add 1 tablespoon red wine vinegar, then season with salt and pepper to taste. If desired, add another 1 tbsp.
- Ladle into bowls, drizzle with olive oil and serve immediately.
- If desired, crumble some feta over the soup before serving.
Tips+: For authentic flavor and texture, use small brown lentils from Greece. Small green lentils also work; on the other hand, avoid Syrian coral lentils because they get crushed when cooked. Lentils do not require pre-soaking; however, it is preferable to rinse them under cold water before cooking and sort them to remove any grit or impurities.
Variation: add fresh spinach 5 minutes before the end of cooking. Season the soup with cumin or ground coriander. Sprinkle with chopped parsley or cilantro. Add a squeeze of lemon juice just before serving or serve with lemon wedges.