In a bowl, whisk together the ¼ cup soy sauce, 2 tbsp honey, 1 tbsp rice vinegar, 1 tbsp plum vinegar, 1 tbsp sesame oil, 1 tbsp hoisin sauce, 1 tbsp chili sauce, 1 tbsp ginger, 2 cloves garlic, 1 tsp cornstarch, and ½ tsp crushed red pepper flakes until smooth. Reserve about ½ cup of the sauce in a separate container for glazing later.
¼ cup soy sauce, 2 tbsp honey, 1 tbsp rice vinegar, 1 tbsp plum vinegar, 1 tbsp sesame oil, 1 tbsp hoisin sauce, 1 tbsp chili sauce, 1 tbsp ginger, 2 cloves garlic, 1 tsp cornstarch, ½ tsp crushed red pepper flakes
Place the 4 salmon fillets in a shallow dish or resealable bag and pour the remaining marinade over the top. Turn the salmon to coat, then cover and refrigerate for at least 30 minutes, or up to 4 hours.
4 salmon fillets
When you're ready to cook, heat a large cast-iron skillet over medium-high to high heat. Add the 1 tbsp sesame oil and the 8 long red peppers. Season with 1/2 tsp salt and cook, turning occasionally, until the peppers are deeply blistered and charred in spots but still have some bite, about 5–7 minutes. The peppers don't need to be completely cooked at this point, they'll finish roasting alongside the salmon.
8 long red peppers, 1 tbsp sesame oil, 1/2 tsp salt
Heat the oven to 400°F. Remove the salmon from the marinade, letting the excess drip off, and arrange the fillets on a parchment-lined sheet pan. Discard the marinade that the raw salmon was sitting in.
Arrange the blistered peppers around the salmon, making sure everything has a little room to roast rather than steam.
Transfer the sheet pan to the oven and bake for about 10–12 minutes, depending on the thickness of your salmon. The peppers should be tender and lightly charred, while the salmon should be cooked through but still juicy in the center.
While the salmon bakes, pour the reserved sauce into a small saucepan. Bring it to a simmer over medium heat and cook for several minutes, stirring often, until it reduces into a thick, glossy glaze.
Remove the salmon from the oven and generously spoon or brush the reduced sauce over each fillet. Scatter the salmon and peppers with sliced 3 scallions and 1 tbsp sesame seeds.
3 scallions, 1 tbsp sesame seeds