Butterscotch Blondie Bars With Peanut-Pretzel Caramel

Preheat oven to 350 °F. Line baking pan with parchment paper, leaving a 1" overhang on long sides of pan. Whisk flour, baking powder, and salt in a medium bowl; set aside. Stir butter in a medium skillet over medium heat until browned bits form at bottom of pan, 7-8 minutes. Transfer to a medium bowl. Add brown sugar. Using an electric mixer, beat until well combined and mixture resembles wet sand, 2-3 minutes. Add eggs and vanilla; beat until fluffy and well combined, about 2 minutes. Add dry ingredients; beat until smooth (batter will be thick). Using an offset or regular spatula, evenly spread batter in prepared pan. Bake blondie until golden brown, edges pull away from sides of pan, and a tester inserted into center comes out with a few moist crumbs attached, 20-25 minutes. Let cool completely in pan on a wire rack.