Heat a heavy skillet (preferably cast iron) over medium-high heat. Add the onions to the skillet and, stirring and tossing frequently to keep them from sticking, cook until golden brown, 7-9 minutes. Scrape into a small bowl. Wipe out the skillet with a paper towel, return to the heat and add the oil. When the oil is hot and coating the bottom of the skillet, add the grated zucchini. Saute for 1-2 minutes, until the zucchini is heated through. Add the browned onions, salt and pepper. Stir. Transfer to a serving bowl.
Per serving: 46 calories, 1.6 grams protein, 6.8 grams carbohydrates, 1.7 grams fiber, 1.9 grams fat (0 grams saturated), 138 milligrams sodium.