Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the peanut butter, sugar, egg, vanilla extract, baking soda, and salt. Mix until well combined and smooth.
Using a tablespoon, scoop out the dough and roll it into balls. Place the dough balls on a baking sheet lined with parchment paper, spacing them about 2 inches apart.
Using the back of a spoon or your thumb, make a small indentation in the center of each cookie. Fill each indentation with about 1/2 teaspoon of fruit preserves.
Bake in the preheated oven for 10-12 minutes, or until the edges are lightly golden.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.