01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, cream softened butter and sugar until light and fluffy using electric mixer or whisk.
03 - Beat in egg, lemon juice, lemon zest, and vanilla extract until well incorporated.
04 - In separate bowl, whisk together flour, baking soda, salt, and poppy seeds until evenly distributed.
05 - Gradually add dry ingredients to wet mixture, mixing until just combined. Avoid overmixing.
06 - Scoop rounded tablespoons of dough onto prepared baking sheets, spacing 2 inches apart.
07 - Bake for 10-12 minutes until edges are lightly golden.
08 - Let cookies cool on pan for 2 minutes, then transfer to wire rack. For optional glaze, mix powdered sugar with lemon juice until smooth and drizzle over cooled cookies.