Preheat the oven to 350 degrees F and fill a large baking sheet with about a quarter-inch of vegetable oil.
Peel the eggplant and slice into quarter-inch thick rounds.
Prepare to dredge the eggplant: Combine egg and water in a shallow dish and beat well, then set aside. Fill a separate shallow dish with Italian breadcrumbs and set aside.
Working one piece at a time, coat the eggplant in the egg wash first, then transfer to the breadcrumbs. Make sure to let any excess egg drip off the eggplant before adding it to the breadcrumbs.Then, coat evenly with breadcrumbs, gently shake off any excess, and then transfer the eggplant to the baking sheet.Repeat until all the eggplant has been coated.
Bake for 20 minutes, flipping halfway through, or until eggplant is tender and both sides are crispy.
Tomato Sauce
While the eggplant is in the oven, make the tomato sauce. First, heat the olive oil in a saucepan over medium heat until shimmering, about 1 minute.
Add the garlic and onion and cook until fragrant, about 30 seconds to 1 minute, stirring frequently. Then, stir in the crushed tomatoes, tomato paste, and water.
Next, stir in the parmesan cheese, garlic powder, onion powder, parsley, basil, oregano, crushed red pepper flakes, and salt.
Bring the sauce to a gentle boil, stirring occasionally, then reduce the heat and simmer for about 10 to 15 minutes. Keep warm until the eggplant is ready.
Assembly
First, spread a layer of tomato sauce in the bottom of a 9x13 baking dish. Then, add a single layer of baked eggplant. Top with another layer of tomato sauce, then sprinkle evenly with about half of the mozzarella cheese.Repeat to build another layer of eggplant, tomato sauce, and mozzarella cheese. Add the parmesan cheese to the top layer.Note that you may not use all of the sauce - use your best judgment and don't be afraid to lay it on thick!
Bake at 350 degrees F for 20 minutes, until the cheese is melted and the eggplant parm is warmed through. Serve hot with an optional side of spaghetti.
Notes
Eggplant: Fresh, in-season eggplant will work best for this recipe. Try to pick out large eggplants that are about 7 to 10 inches in length.Baking dish: Eggplants come in all sizes, so depending on how many slices you get out of your eggplants you may want to change what size baking dish you use. Look at how many slices you have, how many layers you want (we find 2 layers work best), and then pick an appropriately sized dish. You can build 3 layers if you need to, but we would stop there - too many layers, and it starts to fall apart when serving.Serving suggestions: This eggplant parm makes a delicious dinner alongside a small portion of spaghetti. You will probably have some extra tomato sauce from the recipe, so you can use it on top of the pasta (or store it in the fridge for a future pasta night!). Or, make a double batch of the sauce to have plenty extra for your pasta.We also love eating this eggplant parm in sandwiches - just put a few slices on a soft sub roll and enjoy.Storing and reheating: Eggplant parm will stay good in the fridge for up to 5 days in an airtight container. Simply reheat on a microwave-safe plate for about 2 minutes per serving. Make sure to cover it with wax paper or a paper towel to prevent splatter.