Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Add the egg and vanilla extract to the butter mixture and mix until combined.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Roll out the dough on a lightly floured surface into a rectangle about ¼ inch thick.
For the filling, mix together the brown sugar and ground cinnamon. Brush the melted butter over the rolled-out dough and sprinkle the cinnamon-sugar mixture evenly over the top.
Carefully roll the dough into a log, then slice into ½ inch thick rounds. Place the rounds on the prepared baking sheet.
Bake for 10-12 minutes, or until the edges are golden brown. Let the cookies cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.