• Note, you'll need around a quart of marinara sauce already made. Make a batch of Mamma C's marinara sauce without onions a day ahead or use your favorite brand.
• Preheat the oven to 400 degrees F.
• To shred the zucchini, first rinse the whole zucchini squashes and pat them dry. Cut off the stem and root ends and discard those. Use a food processor fitted with the shredding disc (with holes) to shred the zucchini. Or, you can shred the zucchini using the holes on a box grater. Measure out 4 cups of shredded zucchini to use and store any leftovers in the refrigerator or freezer (see notes.)
• Place the shredded zucchini in a colander and sprinkle on ½ teaspoon of salt to draw out moisture. Let it sit for 10 minutes. During this time, grate the Parmesan and Pecorino and shred the provolone or mozzarella.
• After 10 minutes, squeeze handfuls of zucchini over a small bowl (to catch any zucchini that might fall), letting the liquid drip out. Then place the squeezed zucchini onto a clean, lint-free kitchen towel. Start at one short end and roll up the zucchini in the towel, firmly squeezing as you go. Then use paper towels to pat the zucchini dry, squeezing if needed.
• Add the dried zucchini to a large mixing bowl. Use a fork to beat the two eggs in a measuring cup. Pour the beaten eggs into the bowl with the zucchini. Add 1 ½ cups shredded provolone or mozzarella, ½ cup grated Parmesan and ⅛ teaspoon of pepper. Stir to combine. Add the mixture to a greased 9x13 pan.
• Bake the zucchini crust at 400 degrees F for 20 minutes, uncovered, or until it's browned around the edges, golden in the center and firm.

Make the Meat Layer

• While the crust is baking, chop the onion until you have 1 cup. Add the ground beef and chopped onions to a 12-inch skillet. Cook over medium-high heat, breaking up the meat with a wooden spoon. Cook, stirring frequently, until the meat is browned and the onions are tender. Turn off the heat and drain any liquid by tilting the pan and using a spoon to scoop it out to discard.
• Stir in 1 ½ cups of marinara sauce to the meat mixture. Add 1 cup of grated Pecorino and stir to combine. Cook the mixture for a couple of minutes, until it's heated through. Spread the meat mixture evenly on top of the baked zucchini crust.
• Top the meat with ½ cup of shredded provolone or mozzarella in an even layer. Wear oven gloves to transfer the hot pan to the oven. Bake, uncovered, for 10 minutes, or until heated through and the cheese is melted.
• Let the casserole rest for at least 10 minutes before slicing it, so it can set. While it's resting, gently rinse the basil leaves and pat them dry. Stack a few leaves, roll them up, and slice them into ribbons. Serve each portion with some basil sprinkled on top and ladle on some heated tomato sauce.
• Store leftovers in the refrigerator for up to four days. Refrigerate any leftover marinara sauce for up to four days after it was made.