Heat oven to 350°F. Cut a circle of parchment paper to fit in the bottom of a 9 - inch springform pan. Grease the sides with butter.
You will need 3 bowls, 1 large and 2 medium.
Separate the eggs and put the whites in a medium bowl and the yolks in a large bowl.
In a large bowl, beat the egg yolks, lemon zest and 1/4 cup sugar.
In a medium bowl, combine the almond flour and baking powder.
Add the almond flour mixture to the egg yolk mixture and beat until well combined.
In another medium bowl, beat the egg whites until frothy. Add the cream of tartar and salt and continue beating, Add 1/4 cup sugar, one spoonful at a time until soft peaks form.
Gently fold the beaten egg whites into the batter, 1/2 cup at a time. It will seem like it won't combine, but as you add more it will come together and result in a light, airy batter. *If this just won't come together, beat it briefly with an electric mixer. It won't be quite as airy, but it will still be good!
Carefully scoop the batter into the springform pan, smoothing the top. Bake at 350°F for 35 minutes. Remove from oven and let cool completely in the pan. Run a knife around the edge to loosen before releasing the spring. Transfer to serving plate and garnish with fresh sliced strawberries just before serving.