Preheat oven to 350°F. Line a 9x13” pan with foil and spray with nonstick cooking spray.
Cream butter and both sugars with a stand or a hand mixer. Beat in eggs, then mix in vanilla, baking powder, and salt. Slowly stir in flour, mixing until combined.
Spread 2/3 of the batter in the bottom of the prepared pan. The dough is sticky and will make a thin layer. Spray your hands with cooking spray to help ease this process.
Combine filling in a small bowl, sprinkle evenly over bottom layer. Drop 1 tablespoon balls of remaining dough evenly over the top of the filling. Spread lightly with your fingers, it will not cover completely.
Bake for about 20-25 minutes until a toothpick comes out clean from the center. Cool one hour before glazing.
To make the glaze: whisk all ingredients in a small bowl, then frost the bars. Let set before cutting.
Store in an airtight container for up to 3 days.