Place almonds in a food processor and process until finely ground.
Combine the almonds, icing sugar, baking powder and cinnamon in a medium sized bowl. Add the egg yolk and lemon zest and rub together with your fingers to create a crumb line texture.
Whip egg whites to form stiff peaks . add the almond mixture and fold in gently to combine.Shape the mixture into 20 even-sized balls. Arrange the macaroons roughly 2 cm (3/4in) apart on the tray, press an almond in the centre of each and flatten slightly.
Bake for 15 mins or until golden brown. Leave to cool on the tray for 10 mins then transfer to a wire rack to cool completely.
Try not to eat them all by yourself as soon as they come out of the oven!