Preheat oven to 350°F (175°C) and grease a 9×13-inch baking dish.

Grate the zucchini and place it in a colander. Sprinkle with a pinch of salt and let it sit for about 10 minutes. Afterward, squeeze out as much excess moisture as possible using a clean kitchen towel or paper towels.

Prepare the batter: In a large mixing bowl, combine the cornbread mix, eggs, sour cream, milk, melted butter, garlic powder, salt, pepper, and red pepper flakes (if using). Stir until smooth and well combined.

Add zucchini and cheese: Fold in the grated zucchini, shredded cheddar, Parmesan, and finely chopped onions (if using).

Pour into the baking dish: Spread the batter evenly in the prepared dish.

Bake: Place the dish in the oven and bake for 30-35 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.

Cool and serve: Let the casserole cool for 10 minutes before slicing. Serve warm as a side or a vegetarian main dish.
Enjoy.