Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper.

In a large mixing bowl, cream together softened butter and granulated sugar until light and fluffy (about 2-3 minutes).

Beat in the egg, vanilla extract, lemon zest, and lemon juice until fully combined.

In a separate bowl, whisk together flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, mixing until the dough comes together.

Drop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes, or until the edges are slightly golden. Remove and let cool on a wire rack.

While the cookies are cooling, prepare the glaze by whisking together powdered sugar, lemon juice, and lemon zest until smooth.

Once cookies are cool, drizzle the glaze over each one, allowing it to set before serving.