Preheat the oven to 350 F (177 C). Grease a 10 -inch (12 cup capacity bundt pan) with nonstick spray. Use a pastry brush to work the nonstick spray into all the grooves of the pan.
In a large bowl, whisk the flour, baking soda and salt together until well combined.
3¼ cups (390 g) all purpose flour, 2 teaspoons baking powder, ½ teaspoon baking soda, 1 teaspoon salt, ½ teaspoon ground nutmeg
In the bowl of a stand mixer fitted with paddle attachment, beat in the butter and sugar together until light and fluffy. This takes about 2 - 3 minutes at medium speed. On low beat in the eggs and vanilla extract one at a time, waiting until the previous ingredient is just combined before adding the next. Mix until well combined. By hand or on the lowest mixing speed, mix the dry ingredients into the wet alternating with the buttermilk until the batter is just combined. 1¾ cups (350 g) granulated sugar , 1½ cups (338 g) unsalted butter, room temperature, 4 large eggs, room temperature, 1 tablespoon (15 ml) vanilla extract , 1 cup (240 ml) buttermilk, room temperature
Evenly scoop the vanilla donut cake batter into the prepared bundt pan. Bake the donut bundt cake for 45 - 50 minutes or until a toothpick inserted into the center of the pound cake comes out with a few moist crumbs.
Cool the cake in the pan for 10 minutes. Invert the bundt cake pan onto another cooling rack or plate. Then flip the cake upside down one more time so the top is facing up again. Cool the cake completely before topping or serving.
Make the vanilla glaze by whisking the powdered sugar with water, milk and vanilla extract. Pour the glaze on top of the cooled cake donut. Use a pastry brush to apply the glaze to the sides of the cake. Allow 30 - 45 minutes for the glaze to fully set, slice and enjoy.
2 cups (240 g) powdered sugar, 2 tablespoons (30 ml) milk, 1 - 2 tablespoons (15 - 30 ml) water, 1 teaspoon vanilla extract