Pat the salmon dry. Use paper towels to remove surface moisture. Season both sides with salt and pepper. Dry fish sears better and helps the glaze stick.

Mix the glaze. In a small bowl, whisk together orange juice, zest, soy sauce, honey, vinegar, garlic, ginger, and red pepper flakes if using. Taste and adjust sweetness or saltiness.

Preheat your pan. Set a large skillet over medium-high heat and add the oil. When the oil shimmers, it’s ready.

Sear the salmon. Place fillets in the pan, skin-side down if using skin-on. Cook 3–4 minutes until the skin is crisp and the edges turn opaque. Flip and cook 1–2 minutes more. Transfer salmon to a plate (it will finish in the glaze).

Reduce the sauce. Lower heat to medium. Pour the orange mixture into the skillet, scraping any browned bits. Let it simmer 3–5 minutes, stirring, until slightly reduced and glossy. For a thicker glaze, add the cornstarch slurry and simmer 30–60 seconds more.

Glaze the salmon. Return the fillets to the pan. Spoon the sauce over them and cook 1–2 minutes, just until the salmon flakes easily with a fork and the glaze is sticky and clings.

Finish and serve. Remove from heat. Garnish with sliced green onions and sesame seeds. Serve over rice, spooning extra glaze on top.