Preheat your oven to 350°F. Grease an 8″x8″ baking pan and line it with parchment paper.
In a large bowl, whisk together brown sugar, melted butter, and granulated sugar. Add eggs, vanilla, and salt, and whisk until well combined. Stir in flour until just mixed.
Spread 1 1/2 cups of batter in the prepared pan. Add dollops of jam on top and gently spread it over the batter.
Dollop the remaining batter over the jam layer and gently smooth it with an offset spatula.
Bake the blondies for 45 to 50 minutes until golden around the edges. Let them cool completely.
In a medium bowl, whisk powdered sugar and milk until smooth. Pour the glaze over the cooled blondies and spread it evenly. Top with sprinkles and let the glaze set for about an hour.
Cut into bars and enjoy your delightful Pop-Tart blondies!