Make the jam by cooking the frozen blueberries, sugar, lemon zest, juice, and corn starch until thick.
Make the crumb by combining the flour, sugar, brown sugar, and melted butter until combined.
Make the blondie batter by combining the egg, egg yolk, sugar, melted butter, flour, and baking powder.
Spread the blondie batter into an 8x8 baking pan then spread the blueberry jam on top.
Sprinkle the crumble and more blueberries on top, then bake at 350 for 28 minutes.