Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into 1/2-inch thick rounds, lightly brush with half the olive oil, and roast for 20 minutes until tender.
In a large skillet over medium heat, sauté the diced onion and minced garlic in the remaining olive oil until fragrant.
Add the ground lamb to the skillet and cook until browned, then stir in the tomato puree, oregano, cinnamon, sea salt, and black pepper.
Simmer the lamb mixture for 10 minutes over low heat until the sauce has thickened slightly.
In a separate bowl, whisk together the Greek yogurt, egg, and parmesan cheese until the mixture is smooth.
In a small baking dish, layer half of the roasted eggplant, top with the lamb mixture, and then the remaining eggplant.
Spread the yogurt béchamel evenly over the top layer and bake for 15-20 minutes until the topping is set and beautifully golden.