Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish with cooking spray.

Bring a pot of water to a boil; add zucchini. Cook until tender, about 5 minutes; drain. Place in a bowl of cold water until cool, about 5 minutes; drain. Transfer to a large bowl.

Mix 1 cup white sugar, all-purpose flour, lemon juice, apple pie spice, cream of tartar, and salt into the zucchini gently until combined. Pour batter into the prepared baking dish.

Combine cake flour, 1/2 cup white sugar, brown sugar, baking powder, and salt in a bowl. Sprinkle over batter. Drizzle melted butter on top.

Bake in the preheated oven until top is golden brown, about 1 hour.