Preheat your oven to 350°F (175°C). Lightly grease a 9-inch springform pan and line the bottom with parchment paper. Set aside.

Chop the walnuts finely in a food processor until they resemble coarse crumbs, then set aside.

In a clean bowl, beat the egg whites with half of the sugar on high speed until fluffy and doubled in size, about 2 minutes. Set this aside.

In another bowl, combine egg yolks with the remaining sugar and mix until the color lightens and the volume increases, around 2 minutes. If using zest, incorporate it at this stage.

Fold the chopped walnuts into the yolk mixture, then gently incorporate the whipped egg whites using a rubber spatula to maintain the light texture.

Pour the batter into the prepared pan and bake in the preheated oven for 30 to 35 minutes. The cake is done when a toothpick inserted in the center comes out clean.

Cool the cake on a wire rack for 10 minutes, then carefully remove the springform collar. Once cooled completely, dust with powdered sugar, slice, and savor the goodness.