Preheat oven to 350°F and line a baking sheet with parchment paper.
In a large bowl, mix peanut butter, granulated sugar, and brown sugar until smooth.
Add egg and vanilla, mix well.
Stir in baking soda, salt, and flour until just combined.
Scoop tablespoon-sized balls of dough onto the baking sheet, spaced a couple inches apart.
Use your thumb or the back of a spoon to gently press a small indent in the center of each cookie.
Fill each indent with about 1/2 teaspoon of jam.
Gently fold the dough edges up and around the jam, just a little, to help hold it in while baking.
Bake for 10–12 minutes, or until edges are set and tops look slightly crackled.
Let cool on the pan for 5 minutes, then transfer to a rack to finish cooling.