Combine Cucumber And Onion: Combine cucumber and red onion in a large mixing bowl.
In a separate medium bowl, mix together sour cream, mayonnaise, dill, and pepper.
: Transfer dressing to bowl of cucumber and onion and, using a large spoon, toss to coat cucumbers and onions in dressing. Transfer to refrigerator to chill for at least 15 minutes.
Sprinkle on flakey sea salt and, optionally, additional fresh dill and pepper before serving.
