Roll out the pate sucre to a circle about 1/4 inch thick and large enough to slightly overlap a 9-inch metal tart pan. Fit the dough into the pan and trim the edges. Line the bottom and sides of the shell with parchment, or coffee filter papers, or aluminum foil. Fill the lining with dried beans, rice or aluminum beans and bake in the oven for 20 to 25 minutes. Cool and remove the beans and the lining. Return the shell to the oven and bake until golden, 5 to 10 minutes longer.
In a large metal bowl, whisk together the whole eggs, egg yolks, 1 cup sugar, lemon and lime juice, and zests. Set over simmering water and continue to whisk until the mixture is very thick, about 10 minutes.
Turn off the flame and whisk in the butter, a few pieces at a time. (You don't want the mixture to cool down before all the butter is incorporated.) Strain the filling into a bowl. Scrape into the baked tart shell and smooth with a metal spatula. Cool and then refrigerate until firm, 3 to 4 hours, up to overnight.
Sprinkle the remaining 2 tablespoons of sugar evenly over the top of the filling. With a propane blowtorch, caramelize the sugar. (This can also be done under the broiler. Place the tart on the broiler tray directly under the flame, watching carefully to prevent burning). Refrigerate the tart for at least 30 minutes. Or, if desired, eliminate the 2 tablespoons of sugar and arrange circles of raspberries on top of the tart. Sift a little powdered sugar over the berries just before serving.
Cut into slices and serve. If you have caramelized the sugar, serve the tart with fresh strawberries or raspberries.
Yield:2 (9-inch) tart shells
In a food processor fitted with the steel blade, combine the flour and sugar. Add the butter and process until the texture resembles fine meal.
In a small bowl, whisk together the yolks and 1 tablespoon of the cream. Scrape into the machine and process until a ball begins to form, using the additional tablespoon of cream, if necessary. Remove the dough from the machine, and on a lightly floured surface, press down into a circle. Wrap in plastic wrap and refrigerate for at least 1 hour.
Propane gas torches are highly flammable and should be kept away from heat, open flame and prolonged exposure to sunlight. They should be used only in well-ventilated areas. Follow torch manufacturer's instructions for use.