1Preheat the oven to 375°F. Grease a 12-count muffin tin with cooking spray or line with muffin liners.
2Pour the apple cider into a small saucepan and bring it to a gentle simmer over medium heat.
3Let the apple cider cook, stirring every so often, until it’s reduced to about ¼ cup (60g/ml) and slightly darker in color (this will take roughly 20 minutes).
4Pour the reduced apple cider into a heat-safe bowl or a glass measuring cup and let it cool to room temperature before using.
5In a medium bowl, whisk together the cooled apple cider, sourdough discard, melted butter, light brown sugar, egg, applesauce, and grated apples.
6In a separate, larger bowl, whisk together the all-purpose flour, baking powder, baking soda, salt, and apple pie spice.
7Pour the wet ingredients into the dry ingredients and mix together until fully incorporated.
8Scoop the muffin batter evenly into the 12 muffin wells, filling each one about 2/3 full.
9Bake for 22-25 minutes or until a toothpick in the center of the muffins comes out clean.
10Let the muffins cool for 5-10 minutes before transferring them to a wire rack to cool completely.
11In a small bowl, microwave 2 tablespoons of butter in short intervals until fully melted.
12In a separate bowl, combine the granulated sugar and ground cinnamon.
13Dip the tops of each muffin into the melted butter and then dip into the sugar-cinnamon mixture.
For the best results, weigh your ingredients with a kitchen scale for precise, consistent measurements.
Leftover muffins can be stored in an airtight container at room temperature for 3-4 days or in the fridge for up to a week.
To freeze, cool muffins completely, wrap each in plastic wrap, then place in a freezer-safe bag or container and freeze for up to 3 months.
To reheat, thaw frozen muffins at room temperature, then microwave in short 10-second intervals until warm and soft.
To make apple pie spice from scratch, combine 2 and ¼ teaspoons ground cinnamon, ¼ teaspoon ground allspice, ¼ teaspoon ground cloves, and ¼ teaspoon ground nutmeg.