Place the water and lentils in a 5 quart pot and bring to a boil over high heat. Reduce heat to medium, cover, and simmer for 45 minutes, or until the lentils are tender.
Meanwhile, heat the oil in a large skillet over medium-high heat. Add the leek and sauté for a few minutes until it begins to brown. Add the eggplant and 1/2 tsp of salt and sauté for a few minutes, until eggplant begins to soften. Add tomato and cook for a few more minutes, until vegetables become saucy.
Once lentils are just tender, add the saucy veggies, remaining salt, chard or spinach, zaatar, paprika, cumin, bouillon cubes, and lemon zest to the pot. Simmer for another 10 minutes.
Stir in the lemon juice and garlic, ladle into bowls, and serve with lemon slices to garnish.