If you have whole almonds, grind them in a food processor until finely ground. If using almond flour, you can skip this step.

Place the almond flour in a skillet and toast over low heat for about 3 minutes, stirring constantly so it doesn't burn. Remove from heat and let cool.

In a bowl, combine the sugar and eggs. Beat well until the mixture lightens in color.

Wash and dry the lemon, then zest half of it. Add the lemon zest, herbal liqueur, and ground cinnamon to the mixture. Mix well again.

Add the ground almonds to the mixture and fold in with a spatula until well combined.

Preheat the oven to 350°F (180°C), using both top and bottom heat if possible.

Grease a springform pan with the butter and pour in the batter.

Bake the cake at 350°F (180°C) for 35 minutes, until the top is golden brown. For the last 10 minutes, cover with a piece of aluminum foil to prevent burning.

The cake is done when a toothpick inserted in the center comes out clean.

Let the cake cool, then remove it from the pan.