preheat the oven to 400˚
lightly grease your doughnut pans
mix the buttermilk, eggs, melted butter, apple together
stir in sugar, set aside
sift the flour, baking soda, and salt together
stir the wet ingredients into the dry, mix just until incorporated
use a cookie scoop or piping bag to divide the dough between the doughnut compartments
bake at 400˚ for 10-12 minutes
mix the sugar and cinnamon together, if you like more cinnamon add it now
doughnuts are done when they've risen and they bounce back when you poke them, usually between 12-14 minutes
once out of the oven, cool a few minutes and gently remove from the pan
dredge them in cinnamon sugar while they're still warm
sprinkle the last of the cinnamon sugar over them and leve them to cool on a baking rack