Preheat oven to 350℉ (180℃)
Prepare an 8" round cake pan by lightly greasing with butter. Cut a circle of parchment paper to fit in the bottom of the pan.
Combine all-purpose flour and salt in a bowl. Set aside for later.
1 Cup All Purpose Flour, ½ teaspoon Salt
Place sugar, butter and lemon zest in the bowl of a stand mixer fitted with the paddle attachment (a hand mixer may also be used).
⅓ Cup Granulated Sugar, ½ Cup Unsalted Butter, 1 Tablespoon Lemon Zest
Begin mixing the sugar and butter together on medium speed. Continue to mix until the butter and sugar are light and fluffy (2 - 4 minutes), scraping the side of the bowl as needed.
Add the lemon juice and mix until incorporated.
1 teaspoon Lemon Juice
Add flour/salt to the mixing bowl and mix on low speed until just incorporated. The mixture will look crumbly but should hold together when squeezed with your hand.
Stir in the poppy seeds by hand.
2 teaspoons Poppy Seeds
Pour all of the dough into the prepared pan. Using your palms, a dough tamper or a flat-bottomed drinking glass, press lightly on the dough so it is evenly distributed on the bottom of the pan.
Using a sharp knife, lightly score the top of the dough by making 4 lines across the diameter of the pan to form 8 wedges. Be careful not to cut all the way through to the bottom.
Use a dinner fork to gently press impressions into the outer edge of the dough, creating a decorative border.
Bake 22 - 25 minutes. The top will be a light brown and the edges a bit darker.
Allow the pan to cool for 10 minutes on a rack. Carefully turn the pan upside down and release the cookie disk.
Flip the cookie disk over and, using a sharp knife or bench scraper, cut through the scored lines you created before baking. Place wedges on a rack and allow to cool completely before serving.