Preheat oven to 375°F. Lightly grease donut pans.
Whisk together flours, sugars, baking powder, baking soda, nutmeg, cinnamon, salt, and dried buttermilk powder. In another bowl, whisk together eggs, oil, and water
Pour all of the mixed wet ingredients into the large bowl with the dry ingredients. Fold together until batter is smooth and there are no more traces of the dry mixture.
Transfer batter into a large piping bag fitted with a large piping tip. (I used an 18 mm tip) Pipe batter into the donut pans, filling each cavity until half full.
Bake for 10-12 minutes or until cake springs back when lightly touched. Remove from the pan and let cool on rack.