In a food processor (or blender, like I used) pulse flour, powdered sugar, salt and lemon zest until combined.
Add butter and pulse until sandy.
Add egg yolk and lemon juice and pulse until dough comes together.
Remove from food processor and form dough into a 1.5" wide log. Wrap in plastic wrap and freeze until firm. (At least 2 hours, but up until 1 month.)
Preheat oven to 350F degrees.
Remove cookie log from freezer and let sit for about 5 minutes. Cut log in half.
Spread turbinado sugar on a plate; roll cookie log over sugar to coat outside.
Slice log into 1/4" slices and arrange on a parchment-lined baking sheet.
Bake about 13-15 minutes, until cookies are golden brown around edges. Cool completely and ENJOY!