Sponge Cake

INGREDIENTS:

8 egg yolks
1 cup white sugar
1 tablespoon orange zest
¾ cup matzo cake meal
¼ cup potato starch
8 egg whites
½ cup white sugar
1 ½ tablespoons fresh orange juice

DIRECTIONS:

Preheat the oven to 325 degrees F (165 degrees C). Grease and line the bottom of a 10-inch tube pan with parchment paper.
Whisk egg yolks in a medium bowl until lighter in color. Gradually add 1 cup sugar and orange zest; continue whisking until thick and pale, about 7 minutes.
Sift matzo cake meal and potato starch together; set aside.
Beat egg whites in a large glass or metal mixing bowl until foamy. Gradually add remaining 1/2 cup sugar, continuing to beat until whites form stiff peaks. Fold matzo mixture into yolk mixture alternately with orange juice. Fold 1/3 of the whites into the batter, then quickly fold in remaining whites until no streaks remain. Spread evenly into the prepared pan.
Bake cake in the preheated oven, checking after 45 minutes, until a toothpick inserted into the center of the cake comes out clean, about 1 hour. Invert onto a wire rack to cool. Run a knife around the sides of the cake before removing from the pan.