Heat the olive oil in a large pot over medium heat. Add the onion and cook until it softens, about 5 minutes.
Stir in the garlic and diced eggplant. Cook for another 5 minutes until the eggplant begins to soften.
Add the cinnamon and oregano. Stir for 30 seconds to toast the spices.
Pour in the lentils, diced tomatoes, and vegetable broth. Season with salt and black pepper.
Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for 25 to 30 minutes until the lentils are tender.
Taste and adjust seasoning if needed. Serve hot with chopped parsley on top.