Preheat the oven to 350 degrees and line a 12-cup muffin pan with cupcake liners.
In a medium bowl whisk the flour, arrowroot, cinnamon, baking powder and salt to combine.
In medium mixing bowl using an electric mixer with paddle attachment and mix the sugar, milk, oil, egg, vanilla and apple cider vinegar together. Mix for 1-2 minutes until well combined.
Add in the dry mix and mix into a smooth batter. Scrape down the sides of the bowl as necessary.
Divide the batter evenly into the prepared muffin pan and bake for 20-22 minutes until a toothpick inserted comes out clean.
Let the cupcakes cool for 10 minutes in the pan then transfer them to a wire rack to cool completely.
In a small bowl mix the sugar and cinnamon for the topping.
Using a pastry brush to brush a light coating of melted butter over the top of one of them and then dip the top in the bowl of cinnamon sugar. Place it back on the wire rack and repeat this step for the remaining cupcakes.
Prepare the frosting in a mixing bowl using an electric mixer with paddle attachment. Add the butter, cream cheese, cinnamon, vanilla and milk. Cream it together until smooth.
Add in the powder sugar and mix into a smooth frosting. Add a little more milk or powdered sugar to get your desired consistency.
Add the frosting to a piping bag and frost the cupcakes as desired. Let the frosting set.
Serve and Enjoy!