Preheat your oven to 350°F (175°C) and line a 9x13 baking dish with parchment paper.

Whisk three large eggs in a mixing bowl until frothy, about 2 minutes.

Combine granulated sugar, melted butter, lemon juice, lemon zest, vanilla extract, and lemon extract into the whisked eggs. Mix until smooth.

In a separate bowl, whisk together all-purpose flour and baking powder.

Gently stir the flour mixture into the wet ingredients until just combined.

Fold in fresh blueberries carefully to avoid breaking them.

Spread the batter evenly in the prepared baking dish.

Bake in the preheated oven for approximately 30 minutes or until a toothpick comes out clean.

Prepare the blueberry glaze by cooking blueberries and sugar in a saucepan until the blueberries burst.

Pour the warm blueberry glaze over the warm bars and spread evenly.

Let the bars cool completely before cutting into squares.