Preheat the oven to 350°F / 175°C. Line two baking sheets with parchment paper.
In a large bowl, whisk together flour, salt, baking powder, and poppy seeds.
In another large bowl, whisk together the eggs, sugar, oil, vanilla, and lemon zest (if using).
Using a spoon, stir the wet ingredients into the dry ingredients and stir until combined.
Scoop the cookie dough using a #70 (2½-teaspoon) portion scoop onto the prepared baking sheets. You can make the cookies larger or smaller, but it will affect the baking time.
To make the surface perfectly smooth, roll the dough balls between your hands to create a round sphere. Place on the baking sheet, leaving about 1½ inches / 4cm between the cookies. Use the bottom of a glass to press the balls flat to create a ½-inch / 1.3cm tall disk.
Bake, one sheet at a time, in the middle of the oven for 12 to 14 minutes, until the bottoms are golden brown and tops are still pale.
Cool on the baking sheets until completely cool.
Variation: Once the dough is chilled and rolled into balls, press thumb into the dough (almost to the bottom), fill with jam or preferred filling. Roughly 1 cup / 300g of filling.
