Preheat oven to 375°F and line baking sheets with parchment.
Whisk flour, baking soda, and salt in a medium bowl.
Cream butter and sugars until light and fluffy.
Add eggs and vanilla; mix well.
Stir in lemon zest and juice.
Gradually mix in dry ingredients.
Fold in poppy seeds gently.
Scoop dough and place on baking sheet, 2 inches apart.
Bake 9–11 minutes until edges are golden, centers soft.
Cool 5 minutes on sheet, transfer to wire rack.