Using damp fingers, press half the Blondie batter into the bottom of your prepared pan, forming an even layer. If desired, use a third piece of clean parchment to smooth and shape the dough. It is very forgiving and can be easily manipulated.
Once jam comes to room temperature, add it to the blondies. Spread cooled jam into an even layer, all the way to the edges of the batter.
Add remaining blondie batter on top of the cherry jam, pressing into an even layer, and covering all cherry pieces. I like to use my palms to flatten out pieces of dough, arrange them around the pan like puzzle pieces, then smooth the top with a piece of parchment paper. Alternatively, you can quickly chill the dough, then roll out a shape to fit your pan, and place it on top of the jam.
Transfer to preheated oven and bake for 15-20 minutes or until golden brown. The top will appear dried and may have a few small cracks.
Remove from oven, and let cool on a wire rack. Once the pan is cool enough to handle, transfer to the refrigerator to set, at least one hour.
Once set, remove from the refrigerator and using the parchment overhang, pull blondies from the pan. Set on a cutting board and slice into 9 large bars, or 12 smaller bars. It is important to cut the blondies while they're cold, as they get sticky when they warm up. Serve at room temperature, with or without your favorite ice cream.