I added dijon mustard
Make the pickled onions: Place the red onions in a small bowl. Cover with the vinegar and water; let sit for 15 minutes while you prepare the rest of the salad.
Make the dressing: In a bowl large enough to hold the salad, whisk together the vinegar, salt, pepper, honey, garlic, and oregano. Whisking vigorously, slowly pour in the olive oil to form an emulsion.
Assemble the salad: To the dressing, add the cucumber, peppers, tomatoes, olives, and dill.
Drain the red onions and add them to the salad along with the feta. Toss to combine, then taste and adjust seasoning, if necessary. Serve or refrigerate for up to 3 hours. Let the salad sit out at room temperature for about 30 minutes before serving.
