Slice the English cucumbers into thin rounds, about ¼ inch thick, and place them in a colander. Sprinkle generously with salt and let them rest for 30 minutes to 1 hour.

Rinse the salted cucumber slices under cold water to remove excess salt and pat dry with paper towels.

In a mixing bowl, combine sour cream, everything bagel seasoning, white vinegar, and black pepper. Whisk until smooth.

Fold the cucumbers and diced red onion into the dressing, adjusting seasoning to taste.

Serve immediately or refrigerate for at least 30 minutes before serving.