01 - Preheat the oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, cream together the softened butter and sugar until light and fluffy.
03 - Beat in the egg, lemon juice, lemon zest, and vanilla extract until well combined.
04 - In a separate bowl, whisk together the flour, baking soda, salt, and poppy seeds.
05 - Gradually add the dry ingredients to the wet mixture, mixing until just combined.
06 - Scoop rounded tablespoons of dough onto the prepared baking sheets, leaving 2 inches between each.
07 - Bake for 10-12 minutes, or until the edges are lightly golden.
08 - Let the cookies cool on the pan for 2 minutes before transferring to a wire rack to cool completely.
09 - For a glaze, mix powdered sugar with lemon juice until smooth. Drizzle over cooled cookies and let set.