Place fish in a fish poacher or a wide skillet with 4-inch sides. Add enough water to cover the fish. Remove fish to plate and set aside. Add beer, seafood seasoning, peppercorns, lemon juice, and salt to pan. Bring to a boil over medium-high heat. Reduce heat to low. Return fish to pan and poach gently until just cooked through, about 8 minutes for a 1-inch-thick fillet.