Lightly coat eggplant slices with olive oil (I use a pastry brush, dipped and give each side one quick swipe) and arrange on a baking sheet. Bake until softened and golden turning once, 15 to 20 minutes. Reduce oven to 350 degrees F.
In a large saucepan, heat oil over medium heat. Add onion and garlic; cook, stirring occasionally, until onion is translucent, about 5 minutes. Add lentils, tomatoes, and their juices, parsley, oregano, cinnamon, salt, and a pinch of pepper. Bring to a simmer and cook until thickened, about 20 minutes.
While eggplant and lentils are cooking, in a medium bowl, whisk together half-and-half, egg beaters 1/8 cup of the cheese, and nutmeg.
Lightly coat an 8- by 8-inch baking dish with cooking spray. Arrange one-third of the eggplant slices in a single layer in the dish. Spread half of the lentil mixture over the top. Repeat with remaining eggplant and lentil mixture, ending with a layer of eggplant. Pour half-and-half mixture over vegetables and sprinkle with remaining 2 tbsp cheese. Cover with aluminum foil.
Bake moussaka, covered, 20 minutes, then remove foil and bake for 10 to 15 minutes longer, or until heated through and golden on top. Let stand for 15 minutes before cutting. Serve warm. (if you’re freezing this, cut the moussaka into portions prior to freezing) reheats beautifully.