Preheat oven to 350°F and line pans with cupcake liners.
In a large bowl, sift together flour, baking powder, salt and cinnamon. Set aside.
In a stand mixer, combine butter and sugar. Beat for 2 minutes.
Add vanilla extract and egg. Scrape down the sides of the bowl as needed to combine evenly.
Add in half of your dry ingredients (flour mixture) to the wet and then add buttermilk.
Add the remaining dry ingredients and then shredded apples. Mix until until combined.
Fill cupcake liners 3/4 full and bake for 18-25 minutes or until an inserted knife comes out clean.
Let cool.
Peanut Butter Frosting
In a stand mixer, beat butter and peanut butter.
Add vanilla extract, milk, and 1 1/2 cups powdered sugar. Continue to slowly add powered sugar until your reach your desired consistency. If it becomes to thick (like cookie dough) add more milk.
Pipe onto cooled cupcakes and top with apple slices!