2. Sprinkle the shredded zucchini with the salt and let stand for 10 minutes. Drain well until dry (I squeeze my zucchini out in a clean kitchen towel).
3. Stir together the zucchini, shredded cheddar and mozzarella cheeses and the eggs. Once combined, spread the mixture onto the bottom of a 9x13-inch pan. Bake for 20 minutes or until set and golden brown in spots.
4. Meanwhile, brown the ground beef along with the onions and pepper until the beef is cooked through and the vegetables are soft. Stir in the mushrooms, garlic powder and dried oregano. Let simmer together for about 5 minutes. Turn off the heat and stir in the tomato sauce.
5. Spoon the filling onto the prepared zucchini "crust" and top with the shredded mozzarella and Parmesan cheeses. Return to the oven for an additional 10 to 20 minutes, or until the cheese is melted and bubbly.
*Note: Ground beef is optional. It's in the original recipe, but I made this without it because my sister is a vegetarian. If you do make it with the beef, the filling will be thicker and set up a little more, sort of like a high lasagna.