Chop the cucumber into 1 inch slices, then quarter those into large chunks. Very thinly slice the shallot into rings. Mix together the distilled white vinegar and honey. Add a pinch of kosher salt and stir in cucumber. Mix till well-combined. Refrigerate at least 15-20 minutes.
Before serving, stir in the tomatoes and drizzle on olive oil - about 1 teaspoon or to taste. Sprinkle on the sumac and za'atar, adding more on top as needed when serving. When serving, drain the vinegar mixture so it's not included on the plate/dish. Garnish with parsley, if desired.
