Grate the zucchini and mix with 3/4 tsp of the salt. Leave in a bowl for 30 minutes, then squeeze all the liquid out. Meanwhile, chop the onions as finely as you can, then dice the potatoes into 1/4 inch pieces. Finally, chop the tomato.
Heat some oil in a pan measuring about 7-8inches across the bottom. Fry the onion over medium heat for about a minute, then add the potatoes and chili (add more chili if you want it hotter) and fry until potatoes become just soft, 5-10 minutes. Add the zucchini, tomato, cumin, the rest of the salt, cayenne, and a generous amount of black pepper. Stir until tomato becomes soft, about 3 minutes. Remove from heat to let cool.
Thoroughly beat the eggs in a bowl then dump in the cooled vegetables along with some finely chopped parsley or cilantro. Stir everything together, then sprinkle in the baking powder, making sure it dissolves completely, and mix well again.
Wipe clean your fry pan, add the last tablespoon of oil. When the oil is hot, set the temperature to med-low, pour in the egg mixture. Cover the pan (if you don't have a lid, use aluminum foil) and cook for 15-20 minutes or until the center gels. Here's the tricky part. You have to flip the whole pan over. To do this, use a dinner plate, place it over the pan holding it with one hand and use the other to lift and flip the pan. The bottom of the omelette should be a beautiful brown. Now, slide the omelette back into the pan so that the browned part is on top and cook another 5 minutes or so, uncovered. Flip it onto a plate again to serve.