Prep the veggies: Slice zucchini and onion thin (a mandoline slicer works great).

Season and rest: Place them in a large bowl, sprinkle with salt and pepper, then massage by hand for 5 minutes to help release water.

Drain: Place the mixture in a colander over a bowl. Weigh it down with a plate and something heavy (like cans) and let it sit for 2 hours.

Make the batter: Use the drained vegetable liquid to whisk together flour, cornmeal, and 1 tbsp olive oil. Add a splash of water if it’s too thick.

Mix: Combine the batter with the drained zucchini and onion slices.

Prepare baking pan: Line a baking sheet with parchment and lightly oil it.

Spread the mix: Pour the mixture onto the pan, spreading it out evenly. Press it down flat with a spoon or parchment paper.

Top and bake: Drizzle with olive oil, sprinkle with rosemary, and bake at 428°F for 35-40 minutes until golden and crispy.

Cool and slice: Let it cool in the pan for about 1 hour. Slice and serve!