Preheat the oven 350°F. Place cupcake liners in a 12-cavity cupcake pan and set aside.
In a medium mixing bowl, whisk the flour, cocoa powder, baking powder, baking soda and salt until well combined.
In a large mixing bowl, whisk together the peanut butter, oil, sugar, apple cider vinegar, vanilla, and espresso powder, if using. Add the water and whisk well until smooth.
Pour the dry into the wet while stirring until just combined.
Fill each cavity of the cupcake pan ½ way (about ¼ cup of batter in each).
Bake for 18 to 22 minutes until a toothpick inserted in the middle comes out clean.
Let cool in the pan on a wire rack or about 10 minutes before removing the cupcakes from the pan. Let them continue to cool in the liners on the cooling rack.
Once the cupcakes have completely cooled, pipe the Vegan Peanut Butter Frosting, if using, onto each one. If desired, decorate with sprinkles, mini chocolate chips, chopped peanuts, or cacao nibs.