Make the Dressing: In a small mixing bowl, whisk together the apple cider vinegar, balsamic vinegar, olive oil, water, black pepper, and sugar until well combined.
1 cup apple cider vinegar, ½ cup balsamic vinegar, ½ cup olive oil, 2 cups water, 2 teaspoons black pepper, 1 teaspoon granulated sugar
Prep the Vegetables: Quarter the cucumbers, halve the grape tomatoes, and chop the red onion into bite-sized pieces.
6 cucumbers, 2 pints grape tomatoes, 1 red onion
Combine the Salad: Add the cucumbers, tomatoes, red onion, dried dill weed, and crumbled feta cheese to a large mixing bowl.
1 tablespoon dried dill weed, ½ cup crumbled feta cheese
Add the Dressing: Pour the dressing over the salad and gently toss until the vegetables are evenly coated. Use all the dressing if you like a very tangy, marinated salad, or add it gradually if you prefer a lighter coating.
Finish the Salad: Top with extra crumbled feta cheese, then season with salt and additional black pepper to taste.
Salt, Additional black pepper
Chill the Salad: Refrigerate for at least 15 minutes before serving so the vegetables stay cold and the flavors have time to come together.