Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in egg and vanilla extract.
In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to the butter mixture, mixing until combined.
Drop tablespoon-sized portions of dough onto the prepared baking sheets. Make a small indentation in each cookie and swirl in a teaspoon of blueberry jam.
Bake for 10-12 minutes, or until edges are lightly golden. Let cool on the baking sheet for 5 minutes before transferring to a wire rack.
Dust with powdered sugar if desired before serving.