Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, cream the softened butter, granulated sugar, and brown sugar together until light and fluffy, about 3-4 minutes.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Stir in the rolled oats and chopped nuts, if using, until evenly distributed.
Take about 2 tablespoons of dough and flatten it into a disc in your palm. Place a teaspoon of raspberry jam in the center and fold the edges over to seal. Roll it into a ball and place it on the prepared baking sheet. Repeat with the remaining dough.
Bake for 12-15 minutes, or until the edges are lightly golden. Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Once cooled, dust with powdered sugar if desired.