• Begin by preheating your oven to 425°F (220°C). Prepare a 9x13 inch metal baking pan with parchment paper and lightly coat it with olive oil or a nonstick spray to ensure a crispy finish.

For the Vegetables:

• Slice the zucchinis into thin rounds using a sharp knife or mandoline. Toss them in a large bowl with kosher salt and allow them to rest for 15 to 20 minutes to remove excess moisture. After the resting period, wrap the zucchini slices in a clean towel and thoroughly squeeze out any liquid.

For the Batter:

• In a large mixing bowl, combine cornmeal, Parmesan cheese, all-purpose flour, garlic powder, oregano, along with a pinch each of salt and black pepper. Stir until well combined. Then, add in the olive oil and eggs, mixing until the batter thickens.
• Gently fold the drained zucchini slices and thinly sliced onion into the batter, ensuring everything is coated uniformly.
• Transfer the batter into the prepared baking pan and spread it out evenly, pressing down carefully to fill the pan. Bake for about 40 to 45 minutes, until the top is golden brown and crispy.
• Once baked, remove the scarpaccia from the oven and let it sit for approximately 5 minutes. This will allow for easier slicing while keeping it tender. Serve warm, with a squeeze of fresh lemon juice for a bright flavor if desired.