Preheat oven to 160 degrees C. Cut baking paper to line the bottom of a 25cm ring tin. Do not grease.
In a medium bowl, whisk egg yolks until light. Gradually add 250g caster sugar and the orange zest; continue whisking until thick and pale, about 7 minutes. Sift together the matzo meal and potato flour; set aside.
In a large glass or metal mixing bowl, beat egg whites until foamy. Gradually add remaining sugar, continuing to beat until whites form stiff peaks.
Fold the matzo meal into the yolk mixture alternately with the 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 ring tin.
Bake for 1 hour and 10 minutes in the preheated oven, until cake springs back from the touch. Run a knife around the sides of the cake and turn out onto a wire rack to cool.
the best, most moist Passover sponge cake I've ever eaten! - 29 Sep 2008
This is this first sponge cake that I have made that has actually come out perfect!!! Great directions, easy to follow, easy to make. Wonderful taste. Best Sponge Cake I've ever had. - 29 Sep 2008
I used this recipe the last 2 years and I am back to make it again. It is perfect. Just like my gran used to make. I also cut it up to use in other recipes for layers and bottoms, such as trifles and cheesecake. - 29 Sep 2008