Preheat a conventional oven to 180°C (350°F); avoid fan-assisted mode to reduce surface cracking.

Butter the 26 cm round cake tin and line its base with non-stick baking paper.

Wrap the 1 euro coin in non-stick baking paper, then butter and flour the wrapped coin.

Crush the mastic tears with a little granulated sugar until finely ground.

Combine the crushed mastic mixture, remaining granulated sugar, and orange zest in a mixing bowl.

Rub the sugar and orange zest together with your fingertips until fragrant and moist.

Beat the 250 g unsalted butter with the fragrant sugar mixture until pale and fluffy.

Add the 4 eggs one at a time, beating thoroughly after each addition.

Beat in the 2 teaspoons vanilla extract until evenly incorporated.

Sift the all-purpose flour, baking powder, baking soda, and salt together into a clean mixing bowl.

Stir the baking soda into the 90 ml fresh orange juice and allow it to foam.

Beat one-third of the flour mixture into the butter mixture on low speed.

Beat the foaming orange juice mixture into the batter until just combined.

Beat in another third of the flour mixture, then beat in the 180 ml whole milk.

Fold the remaining flour mixture and 180 g roasted almonds into the batter until no dry streaks remain.

Transfer the batter into the prepared cake tin and smooth the surface.

Insert the wrapped 1 euro coin just below the batter surface, keeping it away from the edge.

Bake the cake at 180°C (350°F) for 40 minutes on the center oven rack.

Loosely cover the cake with aluminum foil and bake for another 20 minutes.

Insert a cake tester into the cake; remove it from the oven when the tester comes out clean or with a few moist crumbs.

Cool the cake in its tin for 10 minutes, then transfer it to a cooling rack.

Place the cooled cake on a serving platter and dust it with powdered sugar.

Decorate the cake with fresh fruit before serving and remind guests that it contains a wrapped coin.