How to Make It
Pat salmon dry with paper towels. Sprinkle with salt, and place in a gallon-size ziplock plastic bag.
Stir together lime juice, soy sauce, honey, oil, garlic, ginger, and sesame seeds in a bowl. Pour mixture over salmon in ziplock bag. Seal bag, removing any excess air, and gently massage mixture into salmon. Let stand at room temperature 30 minutes.
Preheat broiler to high with oven rack in upper middle position. Stir together butter, kimchi, and miso in a small bowl. Set kimchi-miso butter aside.
Place salmon on a rimmed baking sheet lined with aluminum foil. Broil until fish flakes easily when tested with a fork, about 8 to 10 minutes.
Top salmon with kimchi-miso butter while salmon is still warm. Scatter scallions evenly over top.