Preheat oven to 375. Simmer lemon juice n a small saucepan over medium heat. Cook until reduced by half. Add 1 stick butter. Stir until melted.
Whisk together flour, baking powder and salt. Cream the other stick of butter with 1 cup sugar on medium speed. Mix in egg and lemon butter. Mix about 3 minutes or until light in color. Mix in vanilla and 2 teaspoons zest. Mix in flour mixture and poppy seeds.
Stir in the remaining sugar, and zest.
Roll into balls. About an inch or so. Roll them into the sugar mixture.Place 2 inces apart on cookie sheet. press with end of glass dipped in sugar mixture. sprinkle with more poppy seeds.
Bake 9 minutes or until the lightly browned along edges. Transfer to wire racks. Cool completely.