Place a colander inside a large bowl. Thinly slice the zucchini using a mandoline or knife, ensuring the slices are very thin but not paper-thin; they should be able to bend when folded in half.

Transfer the sliced zucchini to the colander and sprinkle with kosher salt. Toss to coat and let it drain for at least one hour, though longer is fine.

After draining, press the zucchini firmly in the colander to extract as much water as possible into the bowl below. Reserve this water.

Lay a clean tea towel on a work surface and transfer the zucchini onto it. Gather the towel into a pouch and wring it out over the bowl to remove additional moisture.

Measure the liquid collected and add enough water to make 1 heaping cup (250 grams). Set this mixture aside and dry out the reserved bowl.

Preheat your oven to 425ºF (220ºC). In the reserved bowl, combine the flour, cornmeal, garlic powder, silk chili, and grated parmesan.

Pour the 1 cup (250 grams) of zucchini water into the bowl and whisk until you achieve a pancake-like batter.

Fold the zucchini and sliced onion into the batter using a spatula, ensuring the vegetables are well coated.

Grease a 13×18-inch sheet pan or a 12×16-inch Grandma pan with softened butter. Sprinkle 2 tablespoons of cornmeal over the buttered surface and shake the pan to distribute it evenly.

Spread the zucchini mixture into the pan, pressing it down into a thin layer with your hands.

In a small dish, pour the 2 tablespoons of olive oil and brush it evenly over the top of the mixture. Finish by sprinkling with flaky sea salt.

Bake in the preheated oven for 40 to 45 minutes, or until the edges are crisp. Allow it to cool in the pan for 5 minutes before transferring to a cutting board and cutting into 12 squares.

Serve immediately or let it cool to room temperature before serving.