Pat the salmon dry. Moisture is the enemy of a good sear.
Use paper towels to dry the fillets thoroughly. Season both sides with a pinch of salt and black pepper.
Make the quick hibachi sauce. In a small bowl, stir together 3 tablespoons soy sauce, 1 tablespoon butter (softened), 1–2 teaspoons brown sugar or honey, 1 teaspoon rice vinegar or mirin, 1 minced garlic clove, 1 teaspoon grated ginger, and a few drops of sesame oil. Set aside.
Preheat your pan. Heat a large cast-iron skillet, flat-top griddle, or heavy nonstick pan over medium-high heat until very hot.
Add 1 tablespoon neutral oil and swirl to coat.
Sear the salmon. Place the fillets in the pan, presentation side down (the side that was facing out if skinless). Don’t move them for 3–4 minutes, until a golden crust forms and the fish releases easily.
Flip and lower the heat. Turn the salmon carefully. Reduce heat to medium.
Cook another 2–4 minutes, depending on thickness, until almost at your preferred doneness.
Add the sauce and baste. Drop in the sauce and the remaining 1 tablespoon butter. It will sizzle. Spoon the bubbling sauce over the salmon repeatedly for 30–60 seconds to glaze and finish cooking.
Check doneness. For medium, look for opaque edges and slightly translucent centers, about 125–130°F internal temperature.
Adjust to your preference.
Finish with lemon. Squeeze a little lemon over the fish to brighten the flavors. Sprinkle sesame seeds and sliced scallions.
Serve right away. Plate with rice and quick-sautéed veggies. Spoon any extra pan sauce over the top.