Preheat the oven to 325°F and set an oven rack in the middle position. Spray a 10-inch bundt pan with non-stick cooking spray and dust with flour.
In a medium bowl, whisk together the flour, baking soda and salt. Set aside.
In the bowl of an electric mixer fitted with the paddle attachment (or beaters), cream the butter and sugar on medium speed until light and fluffy, 3-4 minutes. Scrape down the sides of the bowl, then beat in the eggs one at a time, beating well after each addition. Scrape down the sides of the bowl again.
In another bowl, combine the buttermilk, lemon zest and lemon juice.
With the mixer on low speed, beat in one-quarter of the flour mixture, then one-third of the buttermilk mixture. Beat in another quarter of the flour, then another third of the milk mixture. Repeat with another quarter of the flour and the remaining milk mixture. Finally, beat in the remaining flour mixture. Scrape down the sides of the bowl, and give a quick mix to make sure all of the ingredients are well incorporated. Spoon the thick batter into the prepared bundt pan and smooth with a rubber spatula. Bake for 1 hour and 5 minutes, or until a cake tester comes out clean. Cool the cake in the pan for ten minutes on a rack.
Meanwhile, make the syrup. Combine the water and sugar in a saucepan and bring to a boil. Remove from the heat and stir in the lemon juice. Invert the warm cake onto a rack. Slip a large piece of parchment paper or aluminum foil under the rack to catch all the drips from the syrup and glaze. Gradually brush the hot syrup over the cake, letting it soak in (a little syrup will drip off, but try not to rush so that most of it is absorbed). Allow the cake to cool completely, about one hour.
When the cake is cool, make the glaze. Combine the confectioners' sugar, lemon juice, lemon zest and melted butter in a medium bowl, mixing with a fork until smooth. Add more confectioners' sugar or lemon juice as necessary to make a thick but pourable glaze (it should be the consistency of thick honey). Spoon the glaze over the top of the cake, letting it drizzle down the sides.