Bring sauce ingredients to a simmer in a small pan to dissolve sugar. Cool to room temperature.

Place salmon steaks, single layer, in a 9" square pan. Cover with Teriyaki sauce and marinate for 15 minutes.

Blanch carrots and onions in boiling water for 2 minutes. Refresh in a bowl of ice water and drain.

Preheat cast iron skillet over high heat with oil until hot but not smoking. Add salmon to skillet and reduce heat to medium and cook 2 1/2 minutes on each side, turning once until well browned. Transfer to warmed platter.

Add vegetables to skillet and cook one minute. Add remaining teriyaki sauce and bring to a boil, stirring for 1 minutes until thickened. Spoon vegetables and sauce over salmon and garnish with scallions.