Whisk together the cake flour, all-purpose flour, baking powder, baking soda, and salt in a bowl. Set this aside while you work on the wet ingredients. Having this ready ahead of time keeps the whole process moving smoothly.
In a small measuring cup, stir together the sour apple liqueur, cranberry liqueur, and whiskey. This little flavor bomb gets added to the batter in stages later, so keep it close by. It's also the same mixture you'll use again for the frosting.
In your mixer, beat the vegetable oil and sugar together for about a minute until combined. Add in the sour cream and applesauce, mixing until smooth, then scrape down the sides so nothing gets left behind.
Beat in the eggs one at a time until fully incorporated. Add half of your flour mixture and mix on low, then pour in half of your liqueur mixture and stir to combine. Repeat with the remaining flour and liquid until the batter is smooth.
Fill your lined cupcake tin about two-thirds full and bake at 350°F for 16 to 20 minutes. You'll know they're ready when a skewer inserted in the center comes out with just a few moist crumbs.
Let the cupcakes rest in the tin for about 5 minutes before moving them to a wire rack. Don't rush this part, since frosting warm cupcakes will only melt your buttercream into a mess.
Beat the butter and salt until creamy, then slowly add the confectioners' sugar along with your remaining liqueur mixture. Add red food coloring until you reach that deep, glossy poison apple shade, then whip until light and fluffy.
Pipe the frosting into a smooth, rounded dome on each cooled cupcake. Press a candy stem into the top and tuck a candy leaf beside it so each one looks like a little cursed apple ready to be bitten into.