Slice the zucchini and onion in very thin slices using a sharp knife or mandolin slicer. Place them in a large bowl, sprinkle with a little bit of salt, and mix.
See notes section on removing moisture from the zucchini, select method and allot the time needed before resuming the recipe for best results.
Place the zucchini and onions into a clean, thin kitchen towel (like a flour sack towel) or into cheesecloth and WRING it, squeezing out as much water as possible. (If desired, reserve the released water replacing water in the recipe.)
Preheat oven to 400°F. Add the flour, cornmeal, salt, pepper, granulated garlic, basil, rosemary, and Parmesan cheese into another large bowl; mix it all together.
Slowly add the water to the dry goods to make the batter to the consistency of pancake batter.
If using decorative bell pepper rings for the topping, quickly dredge them into the batter, removing any excess batter, and set them aside. By the handful, stir in the zucchini, onions, and bell pepper into the batter.
Line the cast iron with parchment paper (this makes for easy removal for serving.)
Pour in the battered zucchini, pressing it firmly down and smoothing it across the top. Place the reserved bell pepper rings on top.
Brush the entire top with the olive oil.
Place it in the oven, UNCOVERED, and bake for 30-35 minutes or until the top begins to brown.
Notes
How to remove moisture from zucchini?
We want to get as much water as possible out before making this recipe (or many other zucchini recipes.) There are numerous ways to do this, all depending on how much time you have.
Place them either in a bowl or a colander inside a bowl and cover. Leave it overnight in the refrigerator will yield the most released water.
Place in a large bowl then cover with another bowl that can be weighted, causing compression of the zucchini (and onions.) At least 45 minutes is needed but we recommend at least two hours. This compression method can also be used in conjunction with the colander in a bowl method mentioned above.
Once sliced, leave on a cooling rack placed in a baking sheet (to catch the water or you’ll have a mess all over). This method can be done on the counter top for an hour or two, flipping them over at least once or overnight in the refrigerator.
After selecting one of the methods above, before using the zucchini, place into a clean, thin kitchen towel (like a flour sack towel) or into cheesecloth and WRING it, squeezing out as much water as you can.