- Pour 1 cup of apple cider into a small saucepan and simmer over medium heat until it reduces by half, about 10-15 minutes. 
- In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, ground nutmeg, and salt. 
- In a separate bowl, whisk the melted butter, granulated sugar, eggs, vanilla extract, and the reduced apple cider until smooth and well blended. 
- Gradually add the dry ingredients into the wet ingredients, folding gently with a spatula just until combined. Be careful not to overmix; a few lumps are okay. 
- Grease your doughnut pan lightly with butter or a non-stick spray. 
- Spoon the batter into the doughnut pan cavities, filling each about 3/4 full. 
- Bake in a preheated oven at 350°F (175°C) for 12-15 minutes, or until a toothpick inserted comes out clean.