Step 1

Preheat oven to 325° F.

Step 2

Separate the eggs so that the egg whites are in the bowl of an electric mixer and the egg yolks are in a large, separate mixing bowl. Set both bowls aside.

Step 3

In a small bowl, combine half of the sugar with the lemon zest, using your fingertips to press zest into the sugar. Set aside.

Step 4

In a small mixing bowl, sift together the cake meal and the potato starch; whisk in the salt. (If using table salt, sift it with the rest of the dry ingredients.) Set aside.

Step 5

Using an electric mixer, beat the egg whites on medium high speed (6 or 7 on a KitchenAid). Once they start to foam (barely any of the liquid is visible in the center), add 1 teaspoon of the lemon juice. Continue beating, and once the egg whites start to form soft peaks, slowly add the remaining sugar, just a little at a time and keep whisking until stiff peaks form. You may increase the mixer speed to the highest speed once the sugar is fully incorporated.

Step 6

While the mixer is beating the egg whites, add the lemon zested sugar to the yolks and whisk until pale and fluffy. (If you have a hand mixer, feel free to use it. Alternatively, you can whisk or beat the egg yolks with the lemon sugar with the mixer before beating the whites, but be sure to clean the mixing bowl and the beaters very carefully before beating the egg whites.) Whisk in 1 Tablespoon lemon juice and the orange juice.

Step 7

Once the whites have formed stiff peaks, fold in approximately ¼ of the stiff egg whites into the egg yolk mixture. Once fully combined (no streaks remain), carefully add the rest of the egg whites to the bowl and then pour the dry ingredients over the egg whites. Fold just until the whites and dry ingredients are no longer visible.

Step 8

Spread into a 10-inch angel food cake pan, being careful not to overwork the batter to avoid deflating the aerated batter.

Step 9

Bake for 65-70 minutes, until a toothpick inserted comes out clean, the top is nicely browned, and the cake has just started to pull away from the sides of the pan. Remove from oven and invert, allowing cake to cool completely in inverted pan.