Preheat your oven to 180°C (350°F).

In a mixing bowl, beat together the softened butter and sugar until light and fluffy.

Add in the egg, lemon juice, and lemon zest. Mix until thoroughly combined.

In another bowl, whisk together the all-purpose flour, baking powder, and salt. Gradually add these dry ingredients to the wet mixture and stir until a dough forms.

Roll the dough into small balls, about the size of a walnut, then flatten them slightly.

Place a small dollop of prepared lemon filling into the center of half of the flattened dough pieces.

Cover the filled pieces with the remaining flattened dough pieces and seal the edges well.

Place your prepared biscotti on a baking sheet lined with parchment paper.

Bake for 12-15 minutes or until lightly golden brown.

Once baked, allow them to cool on a wire rack. Dust with powdered sugar before serving.