Reduce the cider: Pour the apple cider into a small saucepan.
Simmer over medium heat until reduced to about 1/2 cup, 10–15 minutes. Set aside to cool. This step intensifies the apple flavor.
Prep the oven and pan: Preheat the oven to 350°F (175°C).
Grease a 12-cavity donut pan with nonstick spray or butter.
Mix dry ingredients: In a medium bowl, whisk flours, baking powder, baking soda, cinnamon, nutmeg, cloves (if using), and salt.
Mix wet ingredients: In a large bowl, whisk granulated sugar, brown sugar, melted butter, eggs, vanilla, cooled reduced cider, and buttermilk until smooth.
Combine: Add dry ingredients to the wet. Stir gently with a spatula until just combined. Do not overmix; a few small lumps are fine.
Fill the pan: Spoon the batter into a piping bag or zip-top bag and snip the corner. Pipe batter into each donut cavity, filling about 3/4 full.
Bake: Bake for 10–12 minutes, until the tops spring back lightly and a toothpick comes out clean.
Cool briefly: Let donuts rest in the pan for 5 minutes, then transfer to a wire rack.
Coat: Stir cinnamon and sugar together in a shallow bowl.
Brush warm donuts with melted butter, then roll in the cinnamon sugar to coat all sides.
Serve: Enjoy warm, or let cool entirely before storing.