Season sole with salt, fold into thirds with lemon on top. Place wine in a large, lidded skillet over meduim heat. Arrange in skillet.
Bring wine to a boil; reduce heat to medium-low. Cover; simmer gently until fish is opaque throughout, 3 to 5 minutes. With a spatula, transfer fish to serving plates.
Return liquid in skillet to a boil; cook until reduced to 1/3 cup, 1 to 2 minutes. Add lemon juice; remove from heat. Whisk in butter until smooth. Season with salt; pour over fish; garnish with fresh parsley