Grind the almonds in an electric grinder with a little sugar to prevent them from going oily. With an electric beater, beat the eggs with the rest of the sugar until light and fluffy. (If done by hand, first beat the yolks with the sugar, add the almonds, etc. and finally the egg whites beaten stiff.)
Add the cinnamon and lemon zest then gently fold in the ground almonds. Grease and dust with flour 6-8 individual tart pans; fill them with the mixture and sprinkle with almond flakes. Bake at 350 degrees F for 15 minutes.
Remove from the pans while hot and leave to cool.