Add the cucumbers, onions and salt to a bowl, and stir to combine. Set aside for 30 minutes to draw out any excess moisture. Drain and discard the liquid.
Add the mayonnaise, cider vinegar, dill and sugar to a large bowl; season with pepper and stir to blend. Add the tomatoes and the drained cucumbers and onions, and toss to combine. Taste and adjust the seasoning as needed.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.