In a large bowl, combine the flour, sugar, baking powder, baking soda, cinnamon, salt and mix well.
In a separate bowl, whisk the eggs, and add the buttermilk, butter, and vanilla; whisk until combined.
Add the liquid mixture to the flour mixture, and mix until fully combined.
Add the apples and fold in gently, until the apples are fully incorporated.
Preheat and spray your waffle iron, preparing your waffles as you would normally in your waffler (consult the waffler's instructions if need be).
Once finished, set aside to cool, then cut along the lines into fourths.
To make the glaze
Whisk together the powdered sugar, milk and vanilla extract until fully incorporated.
Dip the cooled and cut doughnuts into the glaze, and let sit on a wire rack over a parchment paper lined cookie sheet for about 20 minutes, to let the glaze drip off and dry before serving.