Melt the butter in the microwave or in a small saucepan over low-medium heat. You don’t want it to bubble, so as to not lose any of the liquid in the butter. Pour the melted butter into a large mixing bowl and let it cool down to room temperature in the fridge. Takes about 20 minutes.
110 g butter
Meanwhile, in a bowl add the granulated sugar and lemon zest. Rub it together to release all of the lemon zest flavor, until it looks like wet sand.
200 g granulated sugar, 1 tablespoon lemon zest
Once the butter has reached room temperature add the lemon granulated sugar and with rubber spatula whisk it together for 1 minute. Alternatively, mix it together in a stand mixer using the paddle attachment.
Add the egg and vanilla extract and mix it in until combined.
1 large egg, 1 teaspoon vanilla extract
In a separate bowl, stir together flour, baking powder, baking soda, poppy seeds and salt. Add the dry ingredients and with a rubber spatula mix it together until combined.
210 g all-purpose flour, ½ teaspoon baking powder, ½ teaspoon baking soda, 1 tablespoon poppy seeds, ½ teaspoon salt
Using a 2 tbsp/ 1.3 ounce/53 g cookie scoop, scoop out 11 cookies and place them on a tray lined with baking paper. Then roll them between your hands into a ball. Place the prepared cookies in the fridge to set for 30 minutes.
Meanwhile, preheat the oven at 180ºC / 355ºF and prepare a baking sheet with baking paper.
Once the 30 minutes has passed, place 6 cookies on a lined baking sheet and put the remaining 5 back in the fridge until the first batch has finished baking. Bake one tray at a time for 10-11 minutes
Once baked, let them cool down on the baking tray for 3 minutes as they still will be soft when they are done. After they have cooled down a bit, use a spatula to lift them onto a cooling rack and let them cool down completely.