Preheat Your Oven: Set it to 350°F (175°C). Grease and flour a 10-12 cup Bundt pan generously to ensure easy cake release.
Prepare Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, nutmeg, and cardamom. Set aside.
Cream the Butter and Sugar: In a stand mixer fitted with the paddle attachment, beat the butter and granulated sugar on medium-high speed for 3-4 minutes until light and fluffy. Scrape down the bowl as needed.
Add Eggs and Vanilla: Add the eggs one at a time, mixing well after each addition. Then, mix in the vanilla extract. The batter might look a bit curdled, but that’s okay— it will come together once you add the dry ingredients.
Combine Wet and Dry Ingredients: Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk and sour cream. Start and end with the dry ingredients. Mix on low speed until just combined—don’t overmix!
Bake: Pour the batter into the prepared Bundt pan, smoothing the top with an offset spatula. Bake for 45-50 minutes or until a toothpick inserted into the center comes out clean. If the top starts to brown too quickly, cover it loosely with aluminum foil.
Cool: Let the cake cool in the pan for exactly 10 minutes. Then, invert it onto a cooling rack or platter. Allow the cake to cool completely before glazing.
Make the Glaze: While the cake cools, whisk together 1 ½ cups powdered sugar and 2-3 tablespoons milk until smooth. Brush the glaze over the cooled cake for that classic donut look and taste.
Set and Serve: Let the glaze set for about 15 minutes before slicing. Then, enjoy your delightful donut cake!