Preheat the oven to 350℉. Line a cookie sheet with parchment paper or a silicone liner.
In a large mixing bowl, stir the peanut butter, butter, eggs, and vanilla together until combined.
Add the cake mix, about ¼ of the package at a time, stirring in between additions. The dough will be pretty thick. It can be easier to mix the dough together with your hands at the end to make sure all of the dry ingredients are incorporated with the wet ingredients.
Use a cookie scoop or spoon to scoop balls of dough uniform in size. (I used a 2.5” cookie scoop.)
Pour the granulated sugar in a small bowl and roll each of the cookie dough balls around in the bowl to coat them in the sugar.
Place the cookie dough balls on the lined cookie sheet. Use a fork to press a criss- cross pattern on the top of the cookie and slightly flatten the dough balls.
Bake the cookies on the middle oven rack in batches for 9-12 minutes or until they are cooked through.
Use a spatula to carefully move the cookies to a cooling rack and enjoy them once they’ve cooled.