Heat the oil in a large pot over medium heat. Add the onions, carrot, and 1/4 teaspoon of salt and cook, stirring occasionally, until they are soft and starting to smell sweet, about 5 to 7 minutes.
Stir in the garlic, cumin, coriander, black pepper, and turmeric, and cook for 30 seconds.
Stir in the lentils and broth. Increase the heat to high and bring just to a boil. Taste, then adjust with salt.
Reduce the heat to a simmer and cook, partially covered, until the lentils are tender, 35 to 40 minutes.
Stir in the kale, chard or spinach, turn off the heat and cover with the lid for 5 minutes.
Add the juice of half a lemon and the fresh herbs. Taste the soup and season with additional salt and lemon juice. For even more lemon flavour, serve with a few lemon slices.