Preheat your oven to 350°F (175°C). Grease and line a 9x13-inch baking pan with parchment paper.

In a large bowl, cream together the butter and sugar until light and fluffy.

Beat in the eggs, one at a time, then add the lemon zest, lemon juice, and vanilla extract. Mix until combined.

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

Spread the dough evenly into the prepared baking pan. Bake for 20-25 minutes, or until the edges are golden and a toothpick inserted into the center comes out clean.

While the bars cool, make the glaze by whisking together the powdered sugar, lemon juice, and zest.

Once the bars are completely cool, drizzle the glaze over the top. Let the glaze set before cutting into squares.