Preheat oven to 350ºF. Line baking sheets with parchment paper.
Add flour, sugar and salt to bowl of stand mixer fitted with the paddle attachment. Beat on low speed for about 30 seconds to combine and aerate the ingredients.
Add the butter and beat on low speed to incorporate. Gradually increase speed to medium-high as the butter breaks up, then beat until mixture resembles coarse crumbs.
Add egg, vanilla and lemon zest (if using). Beat on medium-high until fully incorporated, about 30 seconds. If you have a strong mixer, the dough may come together on its own. If not, dump the crumb-like mixture onto a sheet of parchment paper and gently press and knead it together into a disc.
Roll dough out between sheets of parchment paper to 1/4” thickness.
Dip cookie cutters in flour, then cut shapes out of dough. Use a floured offset spatula to lift the dough cut-outs and transfer to prepared baking sheets.
Bake in center of oven. For 3” cookie shapes, bake 10-12 minutes or until very edges start to turn golden and middles look less shiny. Add 1 minute more for every 1” larger cookie size (or the cookie will have a raw flour taste in the middle).