Start by preheating your oven to 325°F. Butter and flour your bundt pan generously, making sure to coat every groove so the cake releases cleanly later. In a separate bowl, whisk together the flour, salt, baking powder, and baking soda until fully combined.
In your mixer, beat the softened butter and sugar together until the mixture turns pale and fluffy, which usually takes three to four minutes. Add the eggs one at a time, beating well after each one so the batter stays smooth and doesn't curdle.
With the mixer on low speed, add the flour mixture in parts, alternating with the milk. Start and finish with the flour mixture, mixing just until each addition is incorporated. Overmixing at this stage can make the cake dense, so I stop as soon as I see no streaks of flour.
Spoon the batter into your prepared bundt pan and smooth the top gently. Bake for about an hour, or until a toothpick inserted near the center comes out clean. I avoid opening the oven door early since the temperature drop can affect how evenly the cake rises.
While the cake bakes, or right as it comes out of the oven, combine the butter, sugar, and water in a small saucepan over medium heat. Simmer, stirring constantly, until the mixture turns slightly thickened and opaque. Remove it from the heat and stir in the vanilla extract.
Pour the warm glaze evenly over the cake while it's still in the pan, letting it soak into every crevice. Let the cake rest for fifteen minutes before inverting it onto a wire rack. Allow it to cool completely before slicing so the crumb sets properly.