It helps to separate the eggs first, while they are cold, and then let them sit to come to room temperature as you prep the other ingredients. Eggs are easier to separate when cold, and they perform better as leavening agents when at room temperature. When whipping egg whites, make sure your equipment is perfectly clean. Any fat (or even bits of egg yolk in the whites) can keep the egg whites from properly whipping up.
- 4 eggs, separated into 4 egg yolks and 4 egg whites, room temperature (see how to separate eggs)
- 2 Tbsp lemon zest, packed
- 1/2 cup (100 g) white sugar, divided 1/4 cup (50 g) and 1/4 cup (50 g)
- 1 1/2 cup (144 g) finely ground almond flour*
- 1 teaspoon baking powder (make sure your baking powder is fresh!)
- 1/4 teaspoon ground cardamom
- 1 teaspoon white or cider vinegar
- Pinch of salt
- Powdered sugar for sprinkling
* If almond flour is not available at your market, you can grind up blanched, slivered almonds in a food processor until finely ground. I would start with a little more than 1 1/3 cups, perhaps 1 1/2 cups. Our local Whole Foods carries a Bob's Red Mill brand of finely ground almond flour which is what we used for this recipe.
1 Preheat oven, prepare pan: Preheat the oven to 350°F (175 °C). Place a round of parchment paper on the bottom of a 9-inch springform pan, and grease it and the sides of the pan with butter or cooking spray.
2 Beat egg yolks, lemon zest, 1/4 cup sugar: In a large bowl, beat together with a wooden spoon the egg yolks, lemon zest, and 1/4 cup sugar until smooth.
3 Whisk almond flour, cardamom, baking powder, beat into egg yolk mixture: In a separate bowl, whisk together the almond flour, ground cardamom, and baking powder. Add the flour mixture to the egg yolk mixture and beat until smooth.
4 Whip egg whites to soft peaks: With an electric mixer with a very clean bowl and clean whisk attachment, beat the egg whites, starting on low speed and gradually increasing the speed.
When bubbles start to form, add a pinch of salt and the teaspoon of vinegar (both the salt and the vinegar will help the beaten egg whites maintain better structure, as will the sugar in the next step).
As the egg whites begin to increase in volume, sprinkle in the remaining 1/4 cup of sugar, a little at a time, as you continue to beat the eggs whites. Beat until soft peaks form.
5 Fold beaten egg whites into almond mixture: Fold the beaten egg whites into the almond mixture a large scoopful at a time. You won't get much lift with the first third of the egg whites, but as you add more, you'll be able to gently fold in the whites in such a way as to create a light batter.
6 Scoop batter into pan, bake: Gently scoop the batter into a the prepared springform pan and place in the oven. Bake at 350°F (175 °C) for 35 minutes.
Remove from the oven and let cool. Run a sharp knife around the edge of the cake helping it to separate from the side of the pan. Release the springform pan sides, and gently move the cake (on parchment) to a cake serving plate. Sprinkle with a little powdered sugar before serving.