Be sure to read the recipe notes below!
Preheat oven to 350°. Grease a bundt/angel food pan and set aside.
In a stand mixer with the whisk attachment, beat the egg whites until fluffy and a stiff peak forms. Set aside in a separate bowl.
In the stand mixer with the paddle attachment, cream the butter, granulated sugar, and powdered sugar on medium speed until light and fluffy. Add egg yolks and vanilla extract and mix on slow until combined.
In a separate bowl, add flour, baking powder, and salt and mix together.
Add flour mixture and milk, alternately, to the creamed butter and sugar mixture.
Add ½ of the beaten egg whites to the batter and fold in by hand. Once fully incorporated, add the second ½ of the egg whites and fold in by hand until fully combined.
Pour batter into the greased pan and bake for about one hour (can add an extra 10 minutes if needed), until a knife inserted in the center comes out clean.
Let cool completely. (This is important!! The cake should be at room temperature before removing from the pan, slicing, and serving). Transfer cake to a plate or cake stand. Sprinkle the top with powdered sugar and enjoy!