01 - Preheat oven to 350°F and 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 butter, granulated sugar, and lemon zest until light and fluffy, about 2–3 minutes.
04 - Mix in the egg, vanilla extract, and lemon juice until well combined.
05 - Gradually blend in dry ingredients, mixing just until incorporated. Cover and chill dough for at least 15 minutes.
06 - Beat cream cheese, powdered sugar, and vanilla until smooth and creamy. Chill while assembling cookies.
07 - Scoop 1½ tablespoons of dough, flatten into a disc, and place 1 teaspoon of cheesecake filling in center. Top with 1 tablespoon of dough, seal edges, and roll into a ball.
08 - Roll each ball in granulated sugar and extra poppy seeds if desired. Place on prepared baking sheets 2 inches apart.
09 - Bake for 12–14 minutes until edges are lightly golden. Cool on baking sheet for 5 minutes before transferring to wire rack.