Wash and Slice Cucumbers: Begin by rinsing your English cucumber under cold water to remove any dirt. Slice the cucumber into ¼-inch thick rounds, ensuring uniformity for even texture.
Soak the Onions: If you're using white onion, slice it thinly and soak in a bowl of cold water for about 10 minutes.
Prepare the Dressing: In a large mixing bowl, whisk together 1 cup of sour cream (or Greek yogurt), ½ cup mayonnaise, 2 tablespoons of chopped fresh dill, 2 tablespoons of white vinegar, 1-2 teaspoons of granulated sugar, and a pinch of salt.
Combine Ingredients: Once the dressing is perfectly blended, gently add the cucumber slices and drained onion (if using). Toss everything together.
Chill the Salad: Cover the bowl with plastic wrap or a lid and refrigerate for at least 1 hour.
Final Seasoning and Serve: Just before serving, taste the salad and adjust seasoning with additional salt, and a sprinkle of fresh dill if desired.