Prepare Pan: Line a 13x9-inch baking pan with parchment paper. Spread 1 tablespoon olive oil over the bottom and halfway up the sides.
1 tablespoon olive oil
Salt Zucchini: Slice zucchini thin and place in a large bowl. Sprinkle with 1 teaspoon salt, toss, and let sit 15 minutes to draw out water.
2 large zucchini, 2 teaspoons salt
Remove Moisture: Squeeze zucchini over the bowl to release liquid. Place on a towel or paper towels and press out more moisture. Save ¼ cup of the zucchini water for later, topping off with plain water if needed.
Mix Dry Ingredients: Rinse and dry the large bowl. Add rice flour, cornmeal, Parmesan, oregano, 1 teaspoon salt, garlic powder, onion powder, black pepper, and crushed red pepper flakes. Stir to combine.
½ cup rice flour, 1 cup fine cornmeal, 1 ½ cups grated Parmesan cheese, 1 teaspoon dried oregano, ½ teaspoon garlic powder, ½ teaspoon onion powder, ½ teaspoon black pepper, Pinch crushed red pepper flakes
Add Wet Ingredients: Add eggs, ¼ cup olive oil, and reserved zucchini water. Mix until a thick batter forms.
2 large eggs, ¼ cup olive oil, ¼ cup reserved zucchini water
Fold in Zucchini: Stir zucchini slices into the batter until evenly coated.
Spread and Bake: Spread batter into prepared pan, pressing down lightly. Bake at 425°F for 35–40 minutes, until golden and crispy.
Cool and Serve: Cool for 5 minutes. Top with flaky salt, fresh arugula, or a squeeze of lemon juice if desired. Cut into squares and serve warm.