Preheat your oven to 350°F (175°C) to ensure even baking.
Line a 9x13-inch baking pan with parchment paper, allowing for overhang on the sides.
In a mixing bowl, whisk together the all-purpose flour, baking powder, and kosher salt. Set aside.
In another bowl, combine the melted butter with the packed brown sugar and whisk until combined. Add the eggs and vanilla extract, mixing until smooth.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined.
Fold in the Kraft Caramel Bits, semisweet chocolate chips, and broken pretzel pieces until the mixture is thick and chunky.
Pour the batter into the prepared baking pan and spread it evenly. Bake for 25-30 minutes, or until edges are golden and a toothpick comes out with a few moist crumbs.
If desired, sprinkle with flaky sea salt just after removing from the oven.
Let the blondies cool in the pan for at least 15 minutes. Use the parchment overhang to lift them out and cut into squares.