Preheat oven to 400°F and slice eggplant into 1/2-inch rounds.
Arrange eggplant on a baking sheet, drizzle with olive oil, and roast for 15-20 minutes until tender.
Sauté diced onion and minced garlic in a skillet over medium heat until fragrant.
Add ground beef to the skillet and cook until browned, then stir in tomato puree, cinnamon, oregano, sea salt, and black pepper.
Simmer the meat sauce for 5 minutes to allow flavors to meld.
In a bowl, whisk together Greek yogurt, egg, and parmesan cheese until smooth.
Layer half the eggplant in a baking dish, top with the beef mixture, then the remaining eggplant, and spread the yogurt topping over everything.
Bake for 20-25 minutes until the topping is set and bubbling.