Preheat the oven to 180°C (350°F) and line a baking sheet with parchment paper.

Cream the butter and sugar together until light and fluffy.

Add the egg and mix until fully incorporated.

Sift in the flour and baking powder, then mix until a smooth dough forms.

Stir in the orange zest and chopped hazelnuts.

Roll the dough into small balls, place them on the prepared baking sheet, and gently flatten them.

Bake for 12 minutes or until the edges are golden.

Let the cookies cool completely, then dust with powdered sugar if desired.