In a large mixing bowl add softened butter.
Using electric hand beaters, beat butter for a few seconds until creamy.
Sift in icing sugar and beat for 1 minute, scraping down the sides as needed.
Add lemon zest, lemon juice, and vanilla. Beat until well combined for 30 seconds.
Sift over the flour and beat until incorporated and a crumbly dough forms, about 20 seconds. Bring the crumbly dough together with your hands to form a soft dough ball.
Place dough onto a lightly floured bench top or a large floured board.
Roll and work the dough into a 30cm (11-12-inch) length log.
Wrap the log of dough in plastic cling film and transfer it to your refrigerator for 1 hour.
With 30 minutes of chill time remaining for the dough, preheat the oven to 180ºC (356ºF). Line a flat baking sheet with parchment paper and set aside.
Remove the log from the fridge and unwrap it.
Using a sharp knife, slice into individual cookies measuring 1cm (half an inch) in thickness. Place on the lined sheet, leaving a 5cm (2inch) gap between each cookie to allow for spreading. It’s ok if your cookies are not perfectly round.
Bake for 12-15 minutes until lightly golden around the edges but still pale in the middle, ensuring not to over-bake, otherwise, they will not melt in your mouth.
Remove from oven and allow to cool on the sheet for 5 minutes.
Carefully transfer to a wire rack to cool completely.