Line a baking pan that fits inside your oven with parchment paper. Preheat the oven to 300°F (150°C).

Separate the egg yolks from the whites. Beat the egg whites with a mixer until stiff peaks form. While continuing to beat, add the lemon zest, ground cinnamon, egg yolks, and sugar one at a time until well combined. Finally, gently fold in the ground almonds by hand with a spatula.