1 Preheat oven, prepare pan: Preheat the oven to 350°F (175 °C). Place a round of parchment paper on the bottom of a 8 or 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, baking powder, cardamom, 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 well combined. The mixture should resemble a thick paste.

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 egg whites. Beat until soft peaks form.

5 Fold beaten egg whites into almond mixture: Stir a third to a half of the beaten egg whites into the almond mixture to loosen it and make it lighter.

Then gently fold the remaining whipped egg whites into the batter, a large scoopful at a time.

6 Scoop batter into pan, bake: Gently scoop the batter into the prepared springform pan and place in the oven. Bake at 350°F (175 °C) for 30 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.