Adjust the oven rack to the center of the oven and preheat the oven to 350 degrees F.
Line 12 standard muffin cups with paper liners and set aside.
To make the cupcakes: Sift together the cake flour, cocoa powder, baking soda, salt, and baking powder in a bowl.
In the bowl of an electric stand mixer fitted with the paddle attachment, beat together the butter and sugar about 5 minutes until smooth and creamy. Add the egg and beat until fully incorporated. Scrape down the sides of the bowl.
Stir half of the dry ingredients into the butter mixture, the add the milk. Finally stir in the other half of the dry ingredients.
Fill each liner about 1/2 to 2/3 full with cake batter, filling muffin cups evenly. Be careful not to overfill or the batter will overflow a bit when baking. Bake the cupcakes for about 18 to 20 minutes, or until a toothpick inserted into the center comes out clean. Cool cupcakes completely.
To make the buttercream: place 1/2 cup of the wine and the granulated sugar in a small saucepan over medium-high heat and stir until the sugar dissolves. Bring to a boil and then reduce the heat to simmer until the mixture has reduced to about 2 1/2 tablespoons, about 15 to 20 minutes. It should be syrupy. Allow the red wine reduction to cool completely in the refrigerator.
In the bowl of an electric stand mixer fitted with the paddle attachment, beat the butter until nice and fluffy. Pause the mixer occasionally to add the confectioners’ sugar a 1/2 cup at a time and beat until combined (this will prevent the sugar from making too much of a mess when mixing). Beat until fluffy. Carefully add the cooled red wine reduction and salt and continue to beat the frosting until smooth. With the mixer running add the last 1 tablespoon of red wine one at a time and beat until smooth.
If the frosting seems too soft to pipe onto the cupcakes (it may or may not depending on what room temperature is on that given day), place it in the refrigerator briefly for about 10 or 15 minutes (stirring it occasionally) until it gets just firm enough to pipe comfortably (you can also add more confectioners’ sugar, but that will make the frosting a touch sweeter). Fill a pastry bag fitted with whatever large piping tip you prefer with the frosting and frost cupcakes.
Frosted cupcakes can be refrigerated up to 2 days in airtight containers; bring to room temperature before serving.