Begin by dicing the tomatoes and slicing the cucumbers into thin rounds. For the onions, thinly slice them to ensure their flavor is well-distributed in the salad. Gather all the chopped vegetables in a large mixing bowl.

In a separate bowl or jar, combine 1/4 cup vinegar, a pinch of salt, a sprinkle of cracked pepper, and 1 tablespoon of sugar. Whisk until the sugar and salt dissolve completely. Slowly drizzle in 1/4 cup of olive oil while whisking continuously.

Pour the dressing over the vegetable mixture in the large bowl. Gently toss the cucumbers, onions, and tomatoes to ensure every piece is well coated, being careful not to mash the vegetables.

Cover the bowl with plastic wrap and place it in the refrigerator for 15-20 minutes to allow the flavors to marry.

After chilling, give the salad a gentle toss again and taste for seasoning. Adjust with more salt or pepper if needed, then serve either chilled or at room temperature.