Preheat your oven to 400°F (200°C).
Slice the eggplant into half-inch thick rounds and place them on a baking sheet lined with parchment paper.
Roast the eggplant for 15 minutes until softened and lightly browned, then remove from the oven.
While the eggplant roasts, heat the olive oil in 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 wooden spoon, and cook until fully browned.
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 smooth and well combined.
In a small oven-safe baking dish, layer half of the roasted eggplant rounds, followed by the spiced lamb mixture.
Place the remaining eggplant rounds on top of the lamb and pour the yogurt-egg mixture over the entire dish, spreading it to the edges.
Bake for 20 to 25 minutes until the creamy topping is set and has turned a beautiful golden brown.