Heat the oven to 350°F. Line a 9×9-inch baking pan with parchment paper, then lightly cover the lining with nonstick cooking spray. Set the prepared pan aside.

Place the butter in a medium saucepan over medium-low heat and allow it to melt. Continue cooking after the butter begins to boil, swirling the saucepan continuously to prevent burning. Cook until the butter gradually develops an amber-brown color.

Remove the browned butter from the heat. Add the light brown sugar and stir until the mixture is thoroughly combined.

Using a rubber spatula, mix in the eggs, vanilla extract, kosher salt, and baking powder until evenly incorporated.

Stir in the all-purpose flour just until it is fully blended into the batter. Fold in the sweetened coconut flakes last.

Transfer the batter to the prepared 9×9-inch pan and spread it evenly. Bake for 20 minutes, until the edges are golden and the center is nearly set.

Allow the coconut bars to cool completely before slicing them into squares.