Chop 1 English cucumber. Sprinkle with 1 teaspoon kosher salt; let sit 10 minutes. Whisk 1 tablespoon rice vinegar, 2 teaspoons each sugar and soy sauce, 1/2 teaspoon sesame oil, 2 sliced scallions, 1 minced garlic clove and a pinch of red pepper flakes in a large bowl. Drain the cucumber and toss with the dressing; season with salt. Top with chopped cilantro.