In a medium bowl or food processor, whisk
together herb vinegar, sugar, honey, salt, celery seed, dry mustard, and lemon zest.
Add oil in a thin stream, whisking until emulsified. Note: By gradually whisking or blending the oil into the vinegar, you create an
emulsion (a mixture of two liquids that usually don't combine smoothly).
Store, covered, in the refrigerator. Serve at room temperature.