Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius) and line a springform pan with parchment paper.
In a large mixing bowl, beat the egg whites on medium-high speed with an electric mixer for 3-5 minutes until stiff peaks form. Set aside.
6 egg whites
In a separate large bowl, beat the egg yolks, almond flour, granulated sugar, salt, vanilla, and almond extract together on low speed. The batter will be stiff like cookie dough.
Add the beaten egg whites on low speed in 3 additions. The batter will start stiff but loosen to a pourable consistency. During the last addition, gently fold the batter with a rubber spatula until the white streaks of meringue disappear so the batter doesn't deflate.
Pour the batter into the prepared pan. Sprinkle almond slices on top.
40 grams sliced almonds
Bake for 30-35 minutes until a toothpick inserted in the center comes out clean and the top is golden brown.
Take the cake out of the oven and let cool in the hot pan for 10-15 minutes. Gently loosen the sides of the cake from the pan with a butter knife. Then release the pan.
Carefully transfer the cake to a wire rack and let cool completely for 30 minutes. Dust with powdered sugar if desired, slice, and enjoy!
2 teaspoon powdered sugar
Notes
Use cold eggs so the whites and yolks are easier to separate.Let the cake cool completely before dusting with powdered sugar or it'll melt.Storage: Store the flourless almond cake in a large airtight container like a cake carrier for up to 5 days at room temperature.Freezing: Slice the cake and wrap each piece in plastic wrap and a layer of aluminum foil. Place in a freezer bag, freeze for up to 3 months. You can also freeze the cake whole.Let thaw in the refrigerator overnight before bringing to room temperature and enjoying.