Active work time: 25 minutes
Total preparation time: 1 1/2 hours
1/2 cup lemon juice
4 teaspoons grated lemon zest
2/3 cup matzo cake meal
2/3 cup potato starch
8 egg yolks
1 2/3 cups superfine sugar, divided
1/3 cup oil
8 egg whites
1/4 teaspoon salt
Heat the oven to 350 degrees.
Place the lemon juice and grated zest in a small saucepan. Bring to a slow boil. Simmer 4 to 5 minutes. (There should be 6 tablespoons of liquid. If not, add water.) Set aside to cool.
Using a fine-mesh strainer, sift together the matzo cake meal and potato starch 4 times. Set aside.
Place the egg yolks and whole egg in the small bowl of an electric mixer. Beat on medium speed until the mixture begins to thicken, about 3 to 4 minutes. Add 1 cup of sugar, 1 tablespoon at a time, and continue beating until the mixture turns pale yellow and is very thick. Scrape the sides of the bowl occasionally. Slowly add the oil in a steady stream.
Reduce the speed to medium-low. Add the cooled lemon juice and zest and beat until blended. Reduce the speed to low. Gradually add the sifted dry ingredients and mix until the batter is smooth. Transfer to a large mixing bowl. Set aside.
Place the egg whites in the large bowl of a mixer. Using clean beaters or the whip attachment, beat the whites on medium speed until frothy. Add the salt. Increase the speed to medium-high and gradually add the remaining 2/3 cup of sugar at the side of the bowl, beating until soft peaks form.
With a rubber spatula, fold 1/4 of the beaten whites into the yolk mixture to lighten it. Fold in the remaining whites.
Gently pour the batter into an ungreased 10-inch angel food pan with a removable bottom. Smooth the top. Bake in the lower 1/3 of the oven until the cake is golden brown and springy to the touch, 45 to 50 minutes.
Remove the cake from the oven and immediately invert the pan onto a wire rack. Cool the cake completely in the pan. Turn the cake upright and run a thin, sharp knife around the sides of the pan, then around the center tube. Lift the cake by the center tube and remove the ring. Run a knife under the cake to loosen the cake from the pan. Invert the cake and remove the tube section.
Transfer the cake to a platter. Store the cake at room temperature under a glass dome or cover with foil up to 1 week.
14 to 16 servings. Each of 16 servings: 209 calories; 72 mg sodium; 124 mg cholesterol; 7 grams fat; 1 gram saturated fat; 33 grams carbohydrates; 4 grams protein; 0.08 gram fiber.