Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat.

In a medium mixing bowl, combine the peanut butter, sugar substitute, egg, vanilla extract, baking soda, and salt (if using). Mix thoroughly until a smooth dough forms.

Using a tablespoon or cookie scoop, portion out the dough into small balls and place them evenly spaced on the prepared baking sheet.

Flatten each ball slightly with the back of a fork, creating a crisscross pattern on the surface.

Bake in the preheated oven for 10-12 minutes, or until the cookies are lightly golden around the edges.

Remove the baking sheet from the oven and allow the cookies to cool on the sheet for 5 minutes before transferring them to a wire rack to cool completely.