Preheat your oven to 350°F and line two baking sheets with parchment paper.
In a large bowl, mix together the peanut butter, sugar, egg, vanilla extract, baking soda, and salt until well combined and smooth.
Roll the dough into 1-inch balls, then roll each ball in extra granulated sugar to coat.
Place the balls on the prepared baking sheets, spacing them about 2 inches apart.
Use a fork to press down on each cookie ball twice, creating a criss-cross pattern and flattening the dough to about 1/2-inch thick.
Bake for 8-10 minutes until the edges are just set but the centers still look soft.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.