Quadradinhos de Laranja (Little Squares of Orange)

Preheat oven to 350°F. Coat a 9-by-13-inch baking dish with cooking spray. Line with parchment paper, leaving about 1 inch overhanging the long sides. Coat the parchment with cooking spray.

Whisk whole-wheat flour, all-purpose flour, baking powder and salt in a medium bowl.

Beat egg whites in the bowl of a stand mixer with the whisk attachment, or in a large bowl with an electric mixer, on low speed until the whites begin to froth, about 1 minute. Increase the speed to medium and beat until foamy and doubled in size, about 1 minute. Increase speed to medium-high and beat until stiff peaks form, 1 to 2 minutes more. Transfer the egg whites to a clean bowl and set aside.

Wash and dry the mixing bowl (if using a stand mixer, switch to the paddle attachment). Beat 1 1/4 cups sugar and butter in the bowl on medium speed until creamy, 3 to 4 minutes. Add egg yolks one at a time, mixing well after each addition. Beat in orange zest, scraping down the sides as needed. With the mixer on low speed, add the flour mixture, one-third at a time, beating until just combined.

Using a flexible spatula, gently fold the egg whites into the batter. Pour the batter into the prepared pan and spread into an even layer.

Bake until the cake is light golden and the top springs back when touched lightly, 25 to 35 minutes.

Meanwhile, combine orange juice and the remaining 1/3 cup sugar in a small bowl. Stir until the sugar is dissolved.

While the cake is hot, brush with the orange syrup. Let cool for 15 minutes. Lift the cake out of the pan with the parchment and transfer to a cutting board. Cut into 1 1/2-inch squares.