Step 1 In the bowl of a food processor, combine the butter and sugar. Pulse until the mixture resembles coarse, pea-sized crumbs.
Step 2 Add the egg yolk, zest and juice to the bowl and pulse until combined. Add the flour and pulse until the mixture comes together to form a ball. Flatten the dough to one-fourth-inch thickness and wrap in plastic. Freeze for at least 1 or up to 24 hours.
Step 3Remove the dough from the freezer and heat the oven to 375 degrees. Allow the dough to sit at room temperature until it is pliable but still very cold. On a well-floured surface, roll the dough to a one-eighth-inch thickness. Lightly spray 6 (4-inch) tart pans with removable bottoms, and cut out 6 (5-inch) circles. Press the circles of dough into the pans and trim the dough to fit.
Step 4Line the tart shells with foil and fill with dried beans or pie weights. Bake the crusts until the edges are pale gold, about 15 minutes. Remove the foil and pie weights and return the tart crusts to the oven. Bake until the crusts are golden brown, about 5 to 10 minutes. Cool completely before filling.