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