01 - Preheat oven to 350°F. Grease standard donut pan with nonstick spray or softened butter.
02 - Simmer apple cider in a small saucepan over medium heat until reduced to 1/2 cup, about 10 to 12 minutes. Allow to cool.
03 - In a large bowl, whisk together reduced apple cider, maple syrup, applesauce, vegetable oil, eggs, and vanilla extract until blended.
04 - Whisk flour, brown sugar, baking powder, baking soda, cinnamon, nutmeg, and salt in a separate bowl.
05 - Gently fold dry mixture into wet ingredients until just combined. Avoid overmixing to maintain a tender texture.
06 - Spoon or pipe batter into greased donut pan cavities, filling each cavity about three-quarters full.
07 - Bake for 10 to 12 minutes, or until a toothpick inserted in the center emerges clean.
08 - Allow donuts to cool in the pan for 5 minutes, then transfer to a wire cooling rack.
09 - Combine granulated sugar and cinnamon in a shallow bowl for coating.
10 - Brush warm donuts lightly with melted butter. Dip each into cinnamon-sugar mixture to coat evenly.