Preheat oven to 375 degrees.
Prepare the salmon marinade by whisking miso paste, sesame oil, sriracha, rice wine vinegar, sesame oil, honey, and soy sauce (coconut aminos) together in a small bowl.
Place salmon filets in a shallow dish and pour miso sauce over top. Allow to marinade for 20-30 minutes.
While fish marinates, prepare your other ingredients. To make the honey sriracha sauce, mix mayo, sriracha, and honey in a small bowl. Add a teaspoon or so of water to give the sauce a "drizzly" consistency.
Once salmon is done marinating, place each salmon filet in a foil packet with a few spoonfuls of sauce/marinade over top. Seal the packet and bake for 25 minutes.
Start your couscous while fish bakes. Add a tablespoon of butter to a medium pot over medium high heat. Once melted, add scallion whites and cook for 1-2 minutes. Add grated ginger and minced garlic and cook about 30 seconds until fragrant.
Add dry couscous and toss to fully coat in butter and toast slightly, 2-3 minutes. Add 1 ½ cups of water and a big pinch of salt. Bring to a boil, then reduce heat to low. Cover and cook an additional 15-18 minutes until liquid is fully absorbed.
To make your quick pickled red onions, put red onion pieces, 3 tablespoons rice vinegar, and 1 teaspoon white sugar in a microwave safe bowl. Toss to coat fully. Microwave on high for 3 minutes until onions are soft and bright pink. Pour off any excess vinegar and set aside to cool slightly.
When couscous is done, add diced cucumbers and pickled red onions. Add additional salt and pepper as needed.
When salmon is done baking, spoon a teaspoon of cooked marinade over top and remove from foil packet.
To service, place salmon filet over a healthy portion of couscous. Drizzle with honey sriracha mayo, and garnish with scallion greens and optional sesame seeds. Serve immediately.