Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into rounds, brush with olive oil, season with sea salt, and roast for 15 minutes until tender.
While eggplant roasts, heat a skillet over medium heat and sauté the diced onion and garlic until fragrant.
Add the ground lamb to the skillet, breaking it up with a spoon, and cook until browned.
Stir in the tomato puree, dried oregano, and ground cinnamon, then simmer for 10 minutes until the sauce has thickened.
In a small mixing bowl, whisk together the Greek yogurt, egg, and half of the parmesan cheese to create a protein-rich béchamel.
In a small oven-safe baking dish, layer half of the roasted eggplant, followed by the lamb mixture, and the remaining eggplant.
Pour the yogurt béchamel over the top, sprinkle with the remaining parmesan, and bake for 20 minutes until the topping is set and bubbling.