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 blended.
03 - In a large bowl, cream together softened butter and granulated sugar using an electric mixer until light and fluffy, approximately 2 minutes.
04 - Beat in the egg, lemon zest, lemon juice, and vanilla extract until fully incorporated.
05 - Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Take care not to overmix.
06 - Sop tablespoon-sized balls of dough onto the prepared baking sheets, spacing them approximately 2 inches apart to allow for spreading.
07 - Bake for 10 to 12 minutes, or until edges are lightly golden. Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
08 - In a medium bowl, beat softened cream cheese and butter together until smooth. Add powdered sugar, lemon juice, vanilla, and salt. Beat until light and fluffy.
09 - Once cookies have cooled completely, spread or pipe a generous layer of cheesecake frosting onto each cookie. Optionally garnish with additional lemon zest or poppy seeds.