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

Add the egg and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Fold in the lemon zest.

In another bowl, beat the cream cheese until smooth.

Add the powdered sugar, lemon juice, and lemon zest, mixing until well combined.

Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.

Roll the cookie dough into small balls and flatten them slightly.

Place a small amount of lemon filling in the center of half of the flattened dough pieces.

Top with the remaining dough pieces, sealing the edges to encase the filling.

Bake for 10-12 minutes or until the edges are lightly golden.

Allow to cool on the baking sheet for a few minutes before transferring to a wire rack.