Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into half-inch thick rounds, lightly brush with a small portion of the olive oil, and roast for 15-20 minutes until softened.
While the eggplant roasts, heat the remaining 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 up with a spoon, and cook until browned and fully cooked through.
Stir in the tomato puree, dried oregano, ground cinnamon, sea salt, and black pepper, then let the mixture simmer on low for 10 minutes to develop the flavors.
In a small bowl, whisk together the nonfat Greek yogurt, egg, and grated parmesan cheese until the mixture is completely smooth.
In a small oven-safe baking dish, place a layer of roasted eggplant, followed by the lamb mixture, and another layer of eggplant.
Pour the yogurt and egg mixture over the top, spreading it evenly to the edges of the dish.
Bake for 20-25 minutes, or until the custard topping is set and turns a beautiful golden brown.