Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.
Cream softened butter, brown sugar, and granulated sugar until light and fluffy.
Add peanut butter and mix well.
Add egg and vanilla extract; mix until smooth.
In a separate bowl, whisk flour, salt, and baking soda.
Gradually add dry ingredients to the wet mixture; mix just until combined.
Scoop dough into 16 equal balls.
Roll each dough ball in granulated sugar.
Place dough balls on baking sheets.
Flatten each ball with a fork in a crisscross pattern.
Bake for 10 minutes until edges are set and lightly golden.
Let cookies rest on the baking sheet for 3–4 minutes.
Transfer to a wire rack to cool completely.