Marinate the salmon: In a medium saucepan over high heat, cook the pineapple juice, soy sauce, and sherry for 20 minutes. Stir in the brown sugar and cook for 5 more minutes. Using a whisk, stir in miso. Remove from heat and allow the mixture to cool. Season the salmon fillets with the pepper and place them in a shallow baking dish. Pour the pineapple glaze over the salmon fillets, turning to coat each side, and chill for 30 minutes. Preheat oven to 425 degrees F. Roast the fillets: Place the salmon on the top shelf of the oven and cook until the flesh turns opaque -- about 7 minutes. Change the oven temperature setting to broil and cook until the glaze begins to brown -- 2 to 3 minutes. Serve immediately.