Double Lemon Tart

Prepare the crust: Preheat oven to 350 degrees F. In a food processor fitted with a metal blade, combine the flour, sugar, salt, and rosemary. Add butter and pulse until the mixture resembles a coarse meal. Or, by hand, combine the flour, sugar, salt, and rosemary in a bowl. Using your fingers, a pastry cutter, or two knives, mix the butter into the flour mixture until the mixture resembles coarse meal. Place the mixture in an 11-inch tart pan and press it into the bottom and along the side of the pan. Bake the crust until golden brown along the edges -- 15 to 20 minutes. Remove from oven and cool on a wire rack -- about 15 minutes.

Prepare the filling: In a nonreactive pan over medium heat, place lemon sections, juice, and sugar. Stir occasionally until sugar dissolves. Remove the lemon mixture from heat. In a medium bowl, lightly whisk eggs, whites, and salt. While continually stirring, slowly pour the lemon mixture into the eggs. Pour the filling into the cooled crust, arrange lemon slices on top of custard, and bake on the middle rack of the oven until custard is set -- about 30 minutes. If edges begin to overbrown, cover crust with a collar of aluminum foil or pie shields. Cool completely on a wire rack.

Caramelize the tart: Refrigerate the tart to chill it completely. Just before serving, heat an oven broiler and position the rack on the uppermost shelf. Sprinkle the superfine sugar over the chilled tart and place it under the broiler. Watching it closely, as the sugar begins to bubble and brown, carefully rotate it to ensure even browning. Remove the tart once the sugar has caramelized to a golden-brown color -- 2 to 3 minutes. Serve immediately.