Preheat your oven to 350°F (175°C). Grease a 9×9-inch baking pan or line it with parchment paper for easy removal.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large bowl, mix the melted butter and brown sugar until smooth. Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Fold in the butterscotch chips.
Pour the batter into the prepared pan and spread it evenly. Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean. Allow the brownies to cool completely before cutting them into squares.
Notes
Store brownies in an airtight container at room temperature for up to 3 days. For longer storage, wrap individual slices tightly in plastic wrap and freeze for up to 2 months.