2-3drops neon pink liquid food color(I used McCormickbrand)
Preheat oven to 425F. Spray the doughnut pan with nonstick cooking spray.
In a large mixing bowl, sift together the cake flour, sugar, baking powder, salt and nutmeg. Add the buttermilk, eggs, butter and vanilla. Beat until just combined. The batter will be thick. Transfer the batter to a piping bag with a 1/2-inch opening. Pipe the batter into the doughnut cavities until approximately 2/3 full.
Bake the doughnuts for 7 to 9 minutes, or until the top of the doughnuts spring back when touched. Let cool in the pan for 4 minutes. Turn the doughnuts out onto a wire rack to cool completely.
To make the glaze, put the confectioners' sugar in a large bowl. Make a well in the center and add the vanilla extract and 1 tablespoon of milk. Stir together with a whisk; add the food color. Add more milk a little at a time as needed, until a thick glaze is formed. The glaze should fall from a spoon in a thick ribbon back into the bowl, leaving a trail that disappears completely by the count of 10.
Spoon the glaze onto the doughnuts. Garnish with confetti sprinkles. Let the doughnuts stand until the glaze is set, about 30 minutes.
Doughnuts are best served fresh. They can be stored in an air-tight container overnight, and they will still taste fresh, but the glaze will have a wrinkly appearance.