Combine the zucchini and salt in a colander and toss to mix. Set aside to drain for 30 minutes. Squeeze out the excess water. Preheat the oven to 350 F. Grease a 7×11 inch baking dish with butter or lard. (I use a 9×9 inch pyrex dish and reduce the heat to 330.) Stir together the flour and baking powder in a medium bowl. Add the onion, zucchini, cheese, garlic powder and pepper. Mix well with a fork, breaking up any clumps of zucchini. Whisk together eggs and butter in a small bowl. Pour into the zucchini mixture and mix well. Spread evenly in the baking dish. Bake for about 35 minutes, until golden. You want the whole top golden and the entire pan cooked through, so don’t be afraid to give it some extra time if needed. The batter is very thick and moist. Let cool on a wire rack for 5 minutes. Cut into squares and serve warm or at room temperature. Store leftovers (if there are any) in the refrigerator.