Preheat oven to 375ºF (190ºC). Spray the wells of a donut pan*** with non-stick cooking spray.
In a medium-sized bowl, whisk together the cake flour, sugar, baking powder and salt until well blended.
In a separate medium-sized bowl, whisk the buttermilk, egg, melted butter, and lemon zest together until creamy and well combined. Add this mixture to the flour mixture and stir just until combined. Do not over mix.
Transfer the batter to a piping bag or plastic zip bag. Snip off the tip of the bag and pipe batter into the prepared donut pan, filling the wells 2/3 full.
Bake until a toothpick inserted into donuts comes out clean, about 7-8 minutes. Let cool in the pan for a couple of minutes, then remove the donuts to a cooling rack to cool completely.
Prepare Honey Cream Cheese Icing while the donuts are cooling. Dip the tops of the donuts into the icing and decorate as desired. Serve immediately.