Step 1: Prepare Your Pan

1. Preheat the oven to 350°F (175°C).
2. Line the bottom of an 8- or 9-inch springform or round cake pan with parchment paper.
3. Grease the parchment paper and sides of the pan with butter or cooking spray.

Step 2: Separate the Eggs

1. Separate the eggs, placing the whites in the bowl of a stand mixer (or a medium bowl for a hand mixer).
2. Place the yolks in a large mixing bowl.

Step 3: Mix Egg Yolks and Sugar

1. Finely zest the lemons to yield about 2 tablespoons.
2. Add the lemon zest and granulated sugar to the egg yolks. Stir with a wooden spoon or spatula until well combined.

Step 4: Add Dry Ingredients

1. Add almond flour, baking powder, and kosher salt to the egg yolk mixture.
2. Stir until just combined. Some lumps are fine.

Step 5: Whip the Egg Whites

1. Beat the egg whites on medium-high speed until stiff peaks form (about 2–3 minutes with a mixer).
2. The egg whites should be glossy and hold their shape when the whisk is lifted.

Step 6: Fold in the Egg Whites

1. Stir one-third of the whipped egg whites into the almond batter to lighten it.
2. Gently fold in the remaining egg whites in two additions, being careful not to deflate the mixture.

Step 7: Bake the Cake

1. Pour the batter into the prepared pan and spread it evenly.
2. Bake for 25–30 minutes, or until the edges pull away from the pan, the top is golden, and a toothpick inserted into the center comes out clean.

Step 8: Cool and Serve

1. Cool the cake in the pan on a wire rack for 15 minutes.
2. If using a springform pan, release the sides. For a regular cake pan, invert the cake onto a plate, remove the parchment paper, and flip it onto a serving plate.
3. Serve warm or at room temperature, dusted with powdered sugar and garnished with fresh berries if desired.