Prep: 1. Combine vinegar, dijon mustard, honey, salt, and pepper in a jar with a lid and shake well to mix. 2. Add sliced red onion; let pickle for 30 min. 3. Slice cucumber and chop dill. Make: 1. Stir together cucumber and dill in a bowl. Toss with dressing and onions just before serving.
You can save time by not pickling the onions, but if you have time we definitely recommend you give it a try.