Mix the ground almonds, the caster sugar, the salt and baking powder thoroughly in a medium sized bowl and set aside.
250 g ground almonds, 125 g caster sugar, pinch of salt, 1 tsp baking powder
In another bowl, mix the butter and egg yolks together with a wooden spoon for about a minute, you won't get a smooth mixture, don't worry about it.
70 g salted butter, 4 small egg yolks
Add 1 tsp of the lemon juice, lemon zest if using, and orange blossom water and mix again.
1 tsp freshly squeezed lemon juice, zest of 1 lemon, 1 tsp orange blossom water
Add the dry ingredients (almonds, etc) to the egg yolk and butter mixture and stir with the wooden spoon to mix as best as you can.
Finish off with your hands, using only the tip of your fingers as we don't want to knead the dough. Bring it all together, it will be a soft dough.
Form little dough balls, roll them in the icing sugar (if you like, optional) and place on a baking sheet, leaving some space between each cookie. No need to press down, they will naturally spread.
Bake in the preheated oven for about 12-15 minutes, depending on how hot your oven gets. You are aiming for a light, golden colour.
Leave to cool completely before removing from the baking sheet.
Store in an airtight container for up to 2 weeks. You can even freeze them, well covered for up to 3 months.