Beat the butter, sugar, and vanilla sugar (or extract) until creamy. Add the egg yolk and mix briefly until fully incorporated.

Add the flour and salt, then zest the orange directly into the bowl. Mix until a smooth cookie dough forms. Stir in the cranberries and knead lightly to distribute them evenly.

Shape the dough into a log (or two smaller logs about 2 inches / 5 cm in diameter). Wrap in plastic wrap and chill in the fridge for at least 1 hour.

After chilling, slice the dough into rounds and place them on a baking sheet lined with parchment paper.

Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.