Preheat the oven to 350°F (175°C) and line a 12-cup muffin pan with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
In a large bowl, beat the softened butter and sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
Add the dry ingredients alternately with the apple cider and sour cream, beginning and ending with the dry ingredients.
Mix gently until the batter is just combined, being careful not to overmix.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake for 18–22 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.
To make the frosting, beat the softened butter until smooth and creamy.
Gradually add the powdered sugar and cinnamon, mixing until incorporated.
Add the vanilla, salt, and enough cream or milk to reach a smooth, fluffy frosting consistency.
Beat the frosting for 2–3 minutes until light and creamy.
Pipe or spread the cinnamon frosting over the completely cooled cupcakes.
Sprinkle with a little extra cinnamon before serving, if desired.
