01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking powder, baking soda, salt, and poppy seeds in a medium bowl.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2 minutes.
04 - Mix in egg, lemon zest, lemon juice, and vanilla extract until fully incorporated.
05 - Gradually fold dry ingredients into wet mixture, mixing just until combined. Avoid overmixing to prevent tough cookies.
06 - Scoop tablespoon-sized dough balls onto prepared baking sheets, spacing 2 inches apart to allow for spreading.
07 - Bake for 10 to 12 minutes until edges turn lightly golden. Cool on baking sheet for 5 minutes before transferring to wire rack.
08 - Beat cream cheese and softened butter together until smooth and creamy.
09 - Add powdered sugar, lemon juice, vanilla, and salt. Beat until light and fluffy in texture.
10 - Spread or pipe frosting onto completely cooled cookies. Optionally garnish with additional lemon zest or poppy seeds.