Preheat oven to 350°F. Line a baking sheet with parchment paper and set aside.
In a small bowl, combine flour, baking soda, baking powder and salt. Whisk together to combine.
In a medium bowl, using a hand or stand mixer, cream the butter and 3/4 c sugar until light and fluffy, 2-3 minutes. Add in egg yolk, lemon zest, lemon juice, and vanilla, beat again until combined.
Slowly pour in the dry ingredients and beat just until combined, careful not to over mix. Gently fold in the poppy seeds using a rubber spatula. Using a measuring spoon or a cookie scoop, scoop the cookie dough into about 1 1/2 inch balls and roll into the remaining 1/4 cup sugar and place about 2 inches apart on the prepared baking sheet.
Bake 9-11 minutes. They will be very soft at first but they will set up as they cool.
Store in an air tight container or freeze.
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