Spray 12 (3½-inch) tartlet pans* lightly with baking spray. Place tartlet pans on a rimmed baking sheet.
In the work bowl of a food processor, combine flour, granulated sugar, confectioners’ sugar, and salt, plusing to blend. Add cold butter, pulsing until it resembles peas. Add very cold water, pulsing until a dough forms.
Turn out dough onto a lightly floured surface. Divide dough into 2 portions, and shape each portion into a disc. Wrap each portion securely in plastic wrap, and refrigerate for at least 30 minutes.
Preheat oven to 375°.
Working with only one portion at a time, unwrap and place dough on a lightly floured surface. Using a rolling pin, roll dough to a ¼-inch thickness. Using a 4½-inch round cutter, cut 12 rounds from dough, rerolling scraps once. Being careful not to stretch dough, center a dough round atop each prepared tartlet pan. Lightly press dough rounds into bottoms of tartlet pans, and stand dough up against sides of pans. Using a rolling pin, roll over tops of tartlet pans to trim excess dough. Using large end of a chopstick, press dough into indentations in sides of tartlet pans. Place tartlet pans in freezer for 15 minutes.
Coat a 9x12-inch piece of foil with softened butter. Cut foil into 12 (3-inch) squares. Place a foil square, butter side down, in center of each prepared tartlet pan, and place cera-mic pie weights or dried beans atop each foil square.
Bake for 10 minutes.
Carefully remove pie weights and foil. Using a fork, prick bottoms of tartlet shells.
Bake until light golden brown, approximately 15 minutes. Let cool completely before carefully removing tartlet shells from pans.
Divide Lemon Filling among tartlet shells. Place tartlets in a single layer in a covered container, and refrigerate until cold, approximately 2 hours.
Garnish with Sweetened Whipped Cream and Candied Lemon Slices, if desired.
Notes
*We used Gobel 3.5-inch nonstick tartlet pans, available from Sur la Table.
Recipe by TeaTime Magazine at https://teatimemagazine.com/3-lemon-tartlets-recipe/