Slice the eggplants and potatoes into quarter-inch rounds. Sprinkle the eggplant slices with salt and let them sit for 20 minutes to draw out excess moisture. Rinse and pat dry.

Preheat the oven to 400°F. Arrange the eggplant and potato slices on baking sheets, brush with olive oil, and roast for 20 to 25 minutes until tender.

In a large skillet, heat 2 tbsp olive oil over medium heat. Sauté the diced onion until translucent, then add minced garlic and cook for another minute.

Stir in cooked lentils, crushed tomatoes, oregano, and cinnamon. Simmer for about 15 minutes until thickened. Season with salt and pepper.

In a medium saucepan, melt butter over medium heat. Whisk in flour to create a roux, then gradually add milk while whisking. Cook until thickened, then stir in nutmeg, salt, and half of the Parmesan cheese.

In a 9x13 inch baking dish, layer roasted potatoes, eggplant, lentil mixture, and top with another layer of eggplant. Pour béchamel sauce over everything and sprinkle with remaining Parmesan.

Bake at 375°F for 35 to 40 minutes until golden brown. Let rest for 15 to 20 minutes before serving.