Pickled onions adapted from Dolly and Oatmeal. I liked Korean apple vinegar here because it’s almost a drinking vinegar in how gently sweet-tart it is, but apple cider vinegar will work just as well.
for the pickled onions:
1/2 cup water
2 tbsp Korean apple vinegar (or regular apple cider vinegar)
1 teaspoon sugar
1/8 teaspoon salt
1/8 teaspoon black pepper
1 shallot or 2–3 pearl onions, sliced thin
for the rest:
2 cups diced cucumber (I prefer Persian cucumbers for their fresh crunch)
1/4 teaspoon salt
2–3 cups cubed Korean chamoe melon or honeydew
1–2 teaspoons apple vinegar
1/8 teaspoon sesame oil (just a few drops)
1–2 perilla leaves, torn or chopped fine
Salt and black pepper, to taste
An hour or well ahead: Make the pickled onions by combining the water, apple vinegar, sugar, salt, and pepper in a small saucepan and bringing it to a boil over high heat. Lower the heat to medium-low and let simmer gently for 5 minutes. Add the onions, then remove from heat and let sit for an hour before refrigerating or using in the salad.
About 30 minutes ahead: Place the cucumbers in a small bowl and sprinkle 1/4 teaspoon salt over them. Let sit for 30 minutes, refrigerated, to draw out the water.
Drain the cucumbers and pat dry. Add the onions (drained of brine), cubed melon, apple vinegar, sesame oil, and perilla leaves and toss until well-combined. Add salt and pepper to taste, and serve immediately. Enjoy!