Preheat oven to 375 degree F. Spray a 9 x 13 - inch baking pan with oil; set aside.

Use a mandoline to carefully slice the zucchini into ⅛-inch thick slices. Lay onto a wire rack or flat kitchen surface and sprinkle with salt, to draw out extra moisture. After 15 minutes, pat dry with a towel.

For the sauce: In a large saucepan cook beef, onion, and garlic until the meat is brown. Break the meat apart as it cooks.

Add the marinara sauce, basil, oregano, salt, and pepper and stir until combined.

Bring the sauce to a boil then reduce the heat and simmer for 5 minutes, stirring occasionally.

For the ricotta filling: combine the whisked egg, ricotta, Parmesan cheese, and dried parsley.

To layer the keto lasagna: Spread a little sauce on the bottom of the pan. Add a layer of zucchini noodles over the sauce. Spread ⅓ of the ricotta mixture over the zucchini. Then spread ⅓ of the sauce mixture over the zucchini. Sprinkle with ½ cup of mozzarella. Repeat the layers two more times starting with zucchini, following with ricotta, sauce, and mozzarella.

Cover the lasagna pan with foil, place it on a baking sheet and bake for 30 to 35 minutes, or until heated through. Remove the foil, then bake for an additional 10 minutes.

Remove from the oven and let rest for 10 minutes before serving.