How to Make It
Preheat the oven to 350º. 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. Separate the egg yolks and whites. Set whites aside and whisk the yolks together with the lemon zest and 1/4 cup of sugar.
In a separate bowl, stir together the almond flour, baking powder and salt. Add the flour mixture to the egg mixture and combine thoroughly.
In a stand mixer, whisk the egg whites on low, gradually increasing the speed to medium. When the whites begin to froth and increase in volume, slowly add the remaining 1/4 cup of sugar. Increase the speed to medium-high and beat until soft peaks form.
Fold the egg whites into the almond flour mixture and pour into the pan. Sprinkle the top with the almonds and bake for 30 minutes. Remove from the oven and let cool for 10 minutes. Release the springform pan and place the cake on a serving plate. Sprinkle generously with confectioners' sugar and serve.