Preheat your oven to 400°F (200°C). Grease a 9x13-inch baking dish or line it with parchment paper.
Slice zucchini into coin shaped slices. Approximately 1/4 inch in size.
Slice your onions thin.
Saute zucchini and onions in a pan with a little oil for approximately 7-8 minutes.
In a large mixing bowl, combine flour, corn meal, oil, garlic, Italian seasoning, water. salt and pepper. Whisk. Add in the sautéed zucchini and onion. Mix everything together.
Pour the mixture into the prepared baking dish, spreading it out evenly.
Place the dish in the preheated oven and bake for about 40-45 minutes, or until the top is golden brown and the edges are crisp.
Remove the Scarpaccia from the oven and let it cool for a few minutes. Cut it into squares or rectangles to serve.