Step 1

Sprinkle each salmon fillet on all sides with a scant ½ teaspoon salt, rubbing it into the meat and skin. Place the fillets skin side down on a paper towel-lined plate. Refrigerate, uncovered, for at least 4 hours, or up to 24 hours.

Step 2

When ready to cook, in a colander, toss the cucumber and onion with ½ teaspoon salt, gently rubbing until the vegetables wilt slightly. Rinse and pat dry. In a medium bowl, whisk together the vinegar, sesame seeds, gochujang, sesame oil and sugar. Add the cucumber-onion mixture and toss. Taste and season with salt. Cover and refrigerate until ready to serve.

Step 3

Heat the broiler with a rack about 10 inches from the element. Pat the salmon dry on all sides, then brush the flesh side with oil. On a broiler-safe rimmed baking sheet, place the fillets skin side up, spaced at least 1 inch apart. Using the tip of a small, sharp knife, pierce 3 or 4 holes in the skin of each fillet.

Step 4

Broil until the skin is brown and crisp and the flesh flakes easily, 15 to 18 minutes. Transfer to individual plates. Serve with the cucumber salad.