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 until evenly distributed.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2 minutes.
04 - Add egg, lemon zest, lemon juice, and vanilla extract to the butter mixture. Beat until fully combined and smooth.
05 - Gradually add dry ingredients to wet ingredients, mixing until just combined. Avoid overmixing to prevent tough cookies.
06 - Scoop tablespoon-sized balls of dough onto prepared baking sheets, spacing approximately 2 inches apart to allow for spreading.
07 - Bake for 10 to 12 minutes until edges are lightly golden. Allow cookies to rest on baking sheet for 5 minutes before transferring to wire rack to cool completely.
08 - Beat cream cheese and softened butter together until smooth. Add powdered sugar, lemon juice, vanilla, and salt. Continue beating until light and fluffy.
09 - Spread or pipe a generous layer of cheesecake frosting onto each completely cooled cookie. Optionally garnish with additional lemon zest or poppy seeds.