Preheat oven to 325 degrees F.
Grease a 10-inch bundt pan liberally with butter or shortening and dust with flour. Set aside.
Place all the cake ingredients (16 tablespoons butter cut into cubes, 2 cups of sugar, 4 eggs, 1 tablespoon of maple syrup, 3 cups flour, 3/4 teaspoon salt, baking powder, baking soda and buttermilk) in the bowl of your stand mixer fitted with the paddle attachment. Mix on low for 30 seconds and then increase the speed to medium and mix for 3 minutes.
Spread the batter into the prepared pan and bake for 60 - 70 minutes until a toothpick entered into the center comes out clean.
When the cake is done make the glaze. Combine the remaining 5 tablespoons butter, 3/4 cup sugar, bourbon, remaining 1 tablespoon maple syrup and remaining 1/4 teaspoon of salt into a small saucepan over medium-low heat. Stir continuously until the butter is melted and the sugar is dissolved. Do not bring to a boil.
Poke holes all over the warm cake using a knife and pour the glaze evenly on the cake while still in the pan.
Allow the cake to cool completely in the pan and then invert the cake onto a serving plate.