Preheat oven to 350 degrees F (175 degrees C). Grease baking sheets.
Cream the butter with the white sugar and brown sugar. Beat in the egg and vanilla.
Mix the flour and baking powder together. Stir in the flour mixture into the butter mixture and combine.
Form dough into 1 inch balls and place on the prepared baking sheet. Make an indentation in each cookie and fill with jam. Bake at 350 degrees F (175 degrees C) for 12 to 15 minutes. Let cool completely and sprinkle with confectioners' sugar.