Preheat oven to 375°F (190°C).
Sprinkle eggplant slices with salt and let sit for 30 minutes. Rinse and pat dry.
In a skillet, cook ground beef, onion, and garlic until beef is browned. Add tomato sauce, cinnamon, oregano, salt, and pepper. Simmer for 20 minutes.
In another skillet, melt butter and stir in gluten-free flour. Gradually add warm milk, stirring constantly until thickened. Remove from heat and stir in Parmesan cheese and beaten egg yolk.
In a baking dish, layer half of the eggplant slices, then the meat sauce, and then the remaining eggplant slices. Pour the bechamel sauce over the top.
Bake for 45 minutes, until the top is golden brown.
Let cool for 10 minutes before serving.