Line a large baking sheet with parchment paper or a silicone baking mat and set aside. Add butter and icing sugar to a large mixing bowl. Use a handheld mixer, standing mixer, or a wooden spoon to mix them together until smooth.
Add in the vanilla and lemon zest, then add in the flour and mix until combined. If the dough seems too crumbly, add another Tablespoon of butter. If the dough is too soft, add one Tablespoon of flour. Roll the dough into a ball and transfer to a floured surface.
Roll the dough out to about ¼ inch thickness. Use your cookie cutters* to cut shapes out of the dough, then transfer the cookies to the baking sheets. Preheat the oven to 350°F and refrigerate the dough while it preheats.
Once the oven has preheated, bake the cookies (one baking sheet at a time if you are using more than one) until the edges have just slightly started to get a little bit of color, but are still pale, around 9-11 minutes. Don't over-bake! Let them cool on the baking sheet for 5-10 minutes before transferring to a cooling rack.
Lemon Glaze
Once the cookies have cooled completely, whisk the lemon juice, melted butter, and powdered sugar together, then drizzle the glaze over the cooled cookies. Leave the cookies on the rack while the glaze sets.
Video
Notes
PLEASE NOTE: I highly recommend using a kitchen scale to weigh your dry ingredients. Metric measurements are found above, under the "Metric" tab.BUTTER: These cookies have been tested using regular butter, so if you don't follow a vegan diet you can use that!MEASURING FLOUR: Properly measure your flour using the scoop and level method or a kitchen scale. Too much flour will lead to a crumbly dough that is hard to work with. If you accidentally add too much flour, add one additional tablespoon of butter into the dough.COOKIE CUTTERS: These cookies can be made as round cookies or using fun-shaped or holiday cookie cutters. If making the cookies into shapes like Christmas trees or other more intricate shapes, it can help to refrigerate the dough for about 1 hour to help them hold the shape when baking. If you don't have a cookie cutter, you can form the dough into a rectangular log and slice ¼ inch slices or use a cup to cut circles out of the dough! See video for reference.Storage and Freezing Instructions:The cookies should be stored at room temperature in an airtight container for up to a week.Shortbread dough can be frozen for up to 2 months. Before freezing, roll out the cookie dough and cut out the shapes. Place them in a single layer in a parchment-lined container. Add a piece of parchment in between each layer of cookies. Make the glaze after baking the cookies.You can also freeze the baked cookies once the glaze has set, or freeze them not glazed. Freeze in an airtight container with parchment paper between the layers.