Preheat the oven to 350F. Butter and flour a large 15-cup Bundt pan making sure to get into all the crevices.
Sift together the flour, baking soda, and salt into a medium mixing bowl. Set aside.
In another mixing bowl, combine buttermilk, lemon juice, and lemon zest. Set aside.
With an electric mixer fitted with a paddle, cream together the butter and sugar on medium speed until light and fluffy, about 3-4 minutes. Scrape down the sides of the bowl. Add eggs one at a time while scraping the bowl in between each addition.
On low speed, add the dry ingredients to the butter in three additions alternating with the buttermilk mixture, beginning and ending with flour. Scrape the bowl and give it a final mix to thoroughly combine.
Pour the batter into the prepared pan smoothing the top with a spatula.
Bake for 60-65 minutes or until a cake tester comes out clean. Cool in the pan for 15 minutes. Run a small knife around the edge of the pan to loosen the cake and turn out onto a rack. Cool completely.
Whisk together the powdered sugar and lemon juice, adding more sugar or lemon juice to adjust the consistency for a thick but pourable glaze.
When the cake is completely cool, transfer to a serving platter and pour the glaze over the cake.