Preheat the oven to 400 degrees F, ensuring a rack is positioned in the center of the oven. Lightly spritz the surface of a baking sheet with nonstick cooking spray. Set aside. Gather & prep all ingredients according to ingredients list.
Season the entire surface of the salmon fillets well with S&P as desired. Place salmon on the prepared baking sheet, skin side facing down. To a small bowl, add the mayonnaise, shoyu, & prepared wasabi paste (if using), & mix to combine very well. Spread the mixture over each salmon fillet, spreading it so it coats the entire surface of the fish. Sprinkle the furikake over the salmon, covering the mayo mixture thoroughly.
Transfer the prepared salmon to the oven. Bake 12-14 minutes, until the salmon is cooked to your liking & flakes easily when nudge of a fork.