Stir in the baking powder, salt, and flour until just combined.
1/2 teaspoon baking powder, 1 & 1/4 cup all-purpose flour, 1/4 teaspoon salt
Spread the batter evenly into the prepared pan, it will be sticky but just use an offset spatula to spread it as best as you can. Sprinkle with granulated sugar.
extra granulated sugar to sprinkle on top
Bake for 20 minutes, or until the edges are lightly golden and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Allow the bars to cool completely in the pan on a wire rack before slicing.