Preheat oven to 350 degrees, with rack in lowest position. Butter and flour two 4 1/2-by-8-inch (6-cup) loaf pans.
In a small bowl (or liquid measuring cup), combine buttermilk with lemon zest and juice. In a medium bowl, whisk together flour, salt, baking powder, and baking soda.
With an electric mixer, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition.
With mixer on low, add flour mixture in three parts alternately with the buttermilk mixture in two, beginning and ending with flour; beat just until smooth (do not overmix).
Divide batter evenly between pans; smooth tops. Bake until a toothpick inserted in centers comes out clean, 50 to 60 minutes (tent with foil if browning too quickly). Cool 15 minutes in pan. Turn out cakes onto a rack; cool completely before glazing.
Set rack with cakes over a baking sheet lined with waxed paper. Pour glaze over cakes, letting it run down the sides; let dry, about 30 minutes.
The batter can also be baked in a 12-cup buttered and floured nonstick Bundt pan; the cooking and cooling times are the same.