Wash the cucumbers under cool running water, then slice them into thin rounds, set aside in a large mixing bowl.

Thinly slice the red onion and add it to the bowl with the cucumbers.

In a separate bowl, whisk together sour cream, vinegar, sugar, fresh dill, salt, and black pepper until smooth.

Pour the dressing over the cucumber and onion mixture and gently toss to coat.

Cover the bowl and refrigerate for at least 30 minutes to let flavors meld.

Before serving, stir gently, taste, and adjust seasoning if necessary.