In a medium bowl, combine the sliced cucumbers, onions, & tomatoes. Set aside.

In a small bowl, mix together all remaining ingredients EXCEPT sour cream, then slowly whisk mixture into the sour cream until it becomes a creamy dressing.

Pour the Dressing over the vegetables, cover in an airtight container, & refrigerate for a few hours before serving. Flavor of the salad enhances the longer it marinades. Stays fresh 7-10 days in the refrigerator.