Preheat the oven to 350 degrees F. Line two baking sheet with parchment paper or a silicone baking mat. Set aside.

Combine flour, baking powder, and salt in a small bowl. Whisk and set aside.

In a small bowl, add granulated sugar and lemon zest. Rub the sugar and lemon zest together with your fingers, until fragrant.

Using an electric mixer, beat butter and sugar mixture together until light and fluffy. Beat in eggs, lemon juice, and vanilla extract. Mix until smooth.

Slowly mix in dry ingredients on low speed until just combined. Stir in the poppy seeds. Drop dough by tablespoon onto prepared baking sheets, spacing 2 inches apart.

Bake for 12-14 minutes or until cookies are just set and slightly golden brown. Cool cookies on baking sheet for 2 minutes and transfer to cooking racks. Cool completely.

 While the cookies are cooling, make the lemon glaze. In a medium bowl, whisk together powdered sugar and lemon juice. Dip each cookie top into the lemon glaze. Let cookies sit until glaze has set.