Preheat and prepare baking sheets: Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper.
Mix dry ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and poppy seeds.
3 cups all-purpose flour, 1 teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt, 2 tablespoons poppy seeds
Cream butter and sugar: In a large bowl, beat the butter and sugar with an electric mixer until light and fluffy, about 2-3 minutes.
1 cups granulated white sugar, 1 cup unsalted butter
Add wet ingredients: Mix in the egg, vanilla extract, lemon juice, and zest until combined.
1 teaspoon vanilla extract, 2 tablespoons lemon juice, 1 large egg, 1 tablespoon lemon zest
Combine wet and dry ingredients: Gradually add the dry ingredients to the wet ingredients, mixing just until combined.
Scoop and bake: Scoop the dough into 1 ½-inch balls and place them on the prepared baking sheets. Bake for 10-12 minutes, until the edges are set but the centers are still soft. Cool completely.
Glaze the cookies: Mix the icing ingredients in a small bowl. Spread the glaze over the cooled cookies and sprinkle with poppy seeds.
2 cups powdered sugar, 3-4 tablespoons lemon juice, 2 teaspoons lemon zest, poppyseeds