Preheat your oven to 400°F (200°C).
Slice the eggplant into 1/2-inch thick rounds, brush lightly with olive oil, and roast on a parchment-lined sheet for 15 minutes until tender.
While the eggplant roasts, heat a skillet over medium heat and sauté the diced onion and minced garlic until translucent.
Add the ground lamb to the skillet, breaking it apart with a spoon and cooking until browned; drain any excess fat from the pan.
Stir in the tomato puree, dried oregano, ground cinnamon, sea salt, and black pepper, then let the mixture simmer for 5 minutes.
In a small mixing bowl, whisk together the Greek yogurt and the egg until the mixture is completely smooth.
In a small oven-safe baking dish, layer half of the roasted eggplant, followed by the lamb mixture, and then the remaining eggplant.
Pour the yogurt and egg mixture over the top, spreading it evenly to the edges.
Bake for 20-25 minutes until the creamy topping is set and develops a light golden-brown color.