Before assembling the Moussaka, mix in a small amount of the béchamel sauce to the filling. This will help it stay together. I generally don't measure this, but it's approx. 3-5 tbsp.
Lightly grease the baking dish. Using a slotted spoon, add a small amount of filling to the bottom of the pan (this will flavor our vegetables!).
Place the first layout of eggplant to the baking dish.
Add half the amount of the remaining filling on top of the eggplant.
Layer the zucchini (and remaining eggplant if any) on top of the filling.
Layer remaining filling on top of the vegetables.
Pour the keto béchamel sauce on top of the mixture.
Bake the Keto Moussaka for 45 minutes. When there is 15 minutes remaining, remove the moussaka and sprinkle grated Parmigiano-Reggiano cheese. Return to oven and bake for remaining 15 minutes.
Once done cooking , remove the moussaka from the oven and place on a cooling rack. Cover with aluminum foil and let sit for 25-30 minutes. We want the Moussaka to firm up. NOTE: Do not skip this step! This allows the Moussaka to set. If you cut into the dish too soon, it will fall apart.
Serve with a simple or greek salad and enjoy!