Step 1: Reduce the apple cider by simmering it in a small saucepan over medium heat for about 15-20 minutes until it measures exactly 1/2 cup. Let it cool completely.
Step 2: Preheat your oven to 350°F (175°C) and grease a 12-cup muffin tin or line with paper liners.
Step 3: In a medium bowl, whisk together the flour, baking powder, 1.5 tsp cinnamon, nutmeg, cardamom, and salt.
Step 4: In a large bowl, cream together the softened butter, 1/2 cup granulated sugar, and brown sugar until light and fluffy.
Step 5: Beat in the egg and vanilla extract until well combined.
Step 6: Whisk the cooled cider reduction and buttermilk together. Gradually add the dry ingredients to the butter mixture, alternating with the cider/buttermilk mixture, beginning and ending with the dry ingredients.
Step 7: Scoop the batter into the prepared muffin tin, filling each cup about 3/4 full. Bake for 18-22 minutes or until a toothpick comes out clean.
Step 8: While the muffins bake, prepare the coating by mixing the 1/2 cup sugar and 1 tablespoon cinnamon in a small bowl. Melt the 1/2 cup butter in another bowl.
Step 9: Once the muffins are cool enough to handle but still warm, dip the top of each muffin into the melted butter and then generously roll in the cinnamon sugar mixture.