Preheat the oven to 325°F (165°C). Grease and flour a 12-cup Bundt pan or a 10-inch tube pan.

In a large bowl, combine the flour, 2 cups of granulated sugar, salt, baking powder, and baking soda. Mix well.

Add the buttermilk, butter, vanilla extract, and eggs to the dry ingredients. Beat on low speed until the mixture is moistened, then increase the mixer speed to medium and beat for about 3 minutes until the batter is smooth and well combined.

Spoon the batter into the prepared cake pan, spreading it evenly.

Bake in the preheated oven for 55 to 65 minutes, or until a toothpick inserted in the center comes out clean.

While the cake is baking, prepare the sauce. In a small saucepan over low heat, combine the 3/4 cup of granulated sugar, 1/3 cup of butter, water, and vanilla extract. Stir until the butter is melted, but do not bring the mixture to a boil.

Once the cake is out of the oven, transfer it to a wire rack while still in the pan. Use a fork or skewer to pierce the cake all over. Pour the hot butter sauce over the hot cake, allowing it to soak in.

Let the cake cool completely in the pan before inverting it onto a serving plate.