Heat the oven to 350 F.
Grease a 9×13 pan with cooking spray. Set aside.
In a large mixing bowl, beat the melted butter and brown sugar until well combined, about 2 minutes.
Add the eggs, one at a time, until incorporated.
Add the vanilla extract, mixing until combined.
Add the flour, baking powder and salt, mixing with a spatula until combined.
Fold in the chopped pretzels.
Spread the blondie dough into the greased pan.
Drizzle the warm caramel over the dough and swirl with a knife.
Bake for 30-35 minutes, until golden brown and no longer jiggly in the middle.
Cut into squares.