In a medium soup pot, heat olive oil over medium heat. Add onions and sauté with a pinch of salt for 3- 4 minutes, until the onions are translucent.
Add the garlic and cumin and sauté for 1 more minute. Remove half of the mixture from the pot and reserve.
Add the lentils and broth or water to the pot. Bring to a boil, cover, reduce heat to low, and simmer for 45-60 minutes, or until the lentils are tender, adding more water if the soup becomes too thick.
Stir in the greens and simmer for 3 minutes, until the greens wilt but are still a vibrant green.
Remove pan from heat. Add the reserved onions, cayenne pepper, additional sea salt, black pepper, cilantro, and lemon juice.