Shortbread Crust
["1 1/4 c. all-purpose flour", "1/3 c. sugar", "1 tsp. grated lemon zest", "1/4 tsp. salt", "8 Tbsp. unsalted butter, softened and cut into 8 pieces", "1 large egg yolk"]
["You also need a 9-inch pie pan, greased on bottom but not on sides. Dust pan with flour. Tap out excess."]
["flour", "sugar", "lemon zest", "salt", "unsalted butter", "egg yolk"]