01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, salt, and poppy seeds until well combined.
03 - In a large bowl, beat softened butter and granulated sugar with electric mixer until light and fluffy, about 2 minutes.
04 - Beat in egg, lemon zest, lemon juice, and vanilla extract until fully incorporated.
05 - Gradually add dry ingredients to wet mixture, mixing until just 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 are lightly golden. Cool on baking sheet for 5 minutes, then transfer to wire rack.
08 - Beat cream cheese and softened butter in medium bowl until smooth and creamy.
09 - Add powdered sugar, lemon juice, vanilla, and salt. Beat until light and fluffy.
10 - Spread or pipe frosting onto completely cooled cookies. Garnish with extra lemon zest or poppy seeds if desired.