01 -
Preheat oven to 180°C. Grease an 20cm x 20cm baking dish or line with parchment paper.
02 -
Beat softened butter and granulated sugar on medium speed until pale and fluffy, approximately 2 minutes.
03 -
Add egg yolks one at a time, mixing thoroughly after each addition.
04 -
With mixer on low speed, blend in zest and juice from all oranges. The mixture may appear curdled at this stage.
05 -
In a separate bowl, whisk together flour and baking powder.
06 -
With mixer on low speed, gradually incorporate dry ingredients into the butter mixture until just combined.
07 -
In a clean bowl, whip egg whites to stiff peaks. Gently fold one-third of the whipped whites into the batter to lighten, then carefully fold in the remaining whites, taking care not to deflate the mixture.
08 -
Transfer batter to prepared dish. Bake for 35–45 minutes until the surface is springy and a tester inserted into the center emerges clean or with moist crumbs. The internal temperature should reach 88°C.
09 -
Allow cake to cool completely in the pan. Dust with confectioners’ sugar before serving, if desired.