Preheat oven to 180C / 350F / 160C fan forced. Grease and line a 20cm (8 inch) round springform tin with baking paper.
Whisk together the almond meal, baking powder and salt and set aside.
In a medium bowl, whisk the egg whites until soft peak stage and set aside.
Beat the butter and sugar together until light and creamy, then add the yolks and beat well to combine. Add the vanilla, zest and juice and beat until incorporated.
Add the mixed dry ingredients to the butter and egg mixture in 2 parts, and stir gently to combine.
Add 1/3 of the egg whites to the batter and mix through to loosen it. Add the last 2/3 in 2 parts but just fold through gently until all combined. Keep the mixing to a minimum to keep as much air in the mix as possible.
Bake for around 40-45 minutes until golden on top and a toothpick comes out with just a moist crumb or two.
Allow to cool for half an hour before removing the spring form tin. Transfer to a cake plate and allow to cool completely.
FOR THE SIMPLE LEMON ICING
Mix together the icing sugar and half the lemon juice. Slowly add more lemon juice until it gets to the desired consistency, then pour it over the cake.
I use a standard Australian 20ml tablespoon (4 teaspoons worldwide)
All ovens vary - check for doneness 7-8 minutes before the recipe suggests.
Not all baking powders are created equal - double check that yours does not contain gluten if you specifically want this to be gluten free.
For best results you should always weigh ingredients like flour and sugar. Kitchen scales like these are relatively cheap but if you can’t weigh the ingredients, use the spoon and level method (don’t scoop).