Step 1

In a large skillet, combine 3 tablespoons rice vinegar, 2 tablespoons soy sauce, and 2 tablespoons finely grated peeled fresh ginger.

Step 2

Season both sides of 4 skinless cod fillets (6 to 8 ounces each) with coarse salt and ground pepper; place in skillet with vinegar mixture. Bring to a boil; reduce heat to a gentle simmer. Cover; cook until fish is almost opaque throughout, 6 to 8 minutes.

Step 3

Meanwhile, cut green parts of 6 scallions into 3-inch lengths; thinly slice lengthwise. Scatter over fish; cook (covered) until fish is opaque throughout and scallions are just wilted, about 2 minutes more.