Preheat the oven to 350°F.
Grease an 8-inch pan with melted butter or coconut oil, if dairy free (see notes - you can also bake as thin layers as in the photo here).
Beat together the egg yolks, sweetener, salt, vanilla extract, and almond extract until smooth.
Whip egg whites to soft peaks.
Combine the almond flour and baking powder and then stir in the yolk mixture (it will be thick).
Whisk in 1/3 of the egg whites to lighten the yolk/almond flour mixture. Then fold in the remaining whits in two additions, until you have a smooth and fluffy batter with an occasional lump. It will seem like the batter won’t come together but with patient folding, it will.
Spread into the prepared pan and bake for 30 to 35 minutes, or until the cake is golden brown and a toothpick inserted into the center comes out clean.
Remove cake from the oven and allow it to cool in the pan for 5 minutes. Loosen the sides by running a knife around the edge and then turn the cake out to cool completely.
Slice and serve with berries.