Preheat over to 425. Spray doughtnut pan with nonstick cooking spray.
Sift cake flour, sugar, baking powder, nutmeg and salt. Add buttermilk, eggs and butter. Beat until just combined. Fill each doughnut cup 2/3 full.
Bake 7-9 minutes or until top of doughnuts spring back when touched. Let cool in pan 4-5 minutes before removing.