Slice the cucumbers into thin 1/8-inch rounds and halve the onion before slicing it into thin half-moons. Place both vegetables in a large bowl and sprinkle with salt, stirring gently to distribute evenly. The salt will draw out excess moisture from the cucumbers, which is essential for preventing a watery salad later. Let this sit undisturbed at room temperature for 2 hours—I like to cover the bowl loosely so nothing gets into it while the vegetables release their liquid.

Pour the salted vegetables into a colander and let them drain completely for a minute. Rinse them thoroughly under cold running water while gently tossing with your hands to remove the excess salt. Drain well again and return the vegetables to the bowl—this step is crucial because it removes the brine while keeping the vegetables crisp and properly seasoned rather than overly salty.

Pour the heavy cream into the bowl with the drained vegetables, then add the vinegar, fresh dill, and ground white pepper. Fold everything together gently using a rubber spatula, making sure the cream coats all the vegetables evenly. I prefer to dress the salad just before serving because the cucumbers will continue to release a bit of moisture—this keeps the salad from becoming too wet if you need to let it sit.