Preheat your oven to 400°F and line a baking sheet with parchment paper.
Slice the eggplant into half-inch thick rounds, brush both sides with olive oil, and roast for 15 minutes until tender.
While eggplant roasts, heat a non-stick 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 cook until browned.
Stir in the tomato puree, dried oregano, cinnamon, sea salt, and black pepper, then simmer on low for 5 minutes.
In a small bowl, whisk the Greek yogurt and egg white together until completely smooth to create the protein-rich topping.
In a small oven-safe baking dish, layer half of the roasted eggplant slices, followed by the lamb mixture, and then the remaining eggplant.
Spread the yogurt mixture evenly over the top layer and bake for 20 minutes until the topping is set and slightly golden.