How to Make It
In a colander, toss the zucchini with 1 teaspoon salt. Let sit until softened, about 30 minutes; rinse and pat dry.
In a medium bowl, toss the zucchini with the onion, oil, vinegar, ½ teaspoon salt, and ¼ teaspoon pepper. Let sit at least 15 minutes and up to 8 hours before serving.