Place the flour, salt, sugar, rosemary, and the orange zest in a medium bowl and rub the cold butter into it with fingertips or a pastry blender until it resembles very coarse crumbs. Combine the egg, the egg yolk and the liqueur and, with a fork, stir it all into the bowl with the flour mixture, forming a rough paste.
Turn it out onto a lightly flowered work space and, with a few short strokes, form the mixture into a dough. flatten the dough into a disc, wrap it tightly in plastic wrap and place it in the freezer for 20 minutes. press the rested, chilled dough over the surfaces of a buttered 12- to 14-inch tart pan with a removable bottom. cover the pastry-lined tin in plastic wrap and chill it again, for twenty minutes, in the freezer.
Preheat the oven to 400 degrees.
With a fork, prick the chilled pastry over its surface and bake it for 10 minutes. lower the temperature to 375 degrees and continue baking the pastry for an additional 5 or 6 minutes or until it is firm and barely beginning to take on some color. Cool the pastry thoroughly on a rack. Proceed with the orange cream.
For the filling:
If the oven is not already hot, preheat it to 400 degrees. In a medium bowl, beat together the orange juice, the zest, the sugar, and the mascarpone, amalgamating the ingredients as well. add the eggs, one at a time, beating vigorously, incorporating each before adding the next. add the liqueur and beat thoroughly.
Pour the orange cream into the prepared pastry and bake the tart for 20 to 25 minutes or until the cream is just firmed and has taken on patches of burnished skin and the crust is deeply golden.
Cool the tart on a rack for 15 minutes before removing its ring and permitting it to cool thoroughly. Thickly dust the tart with confectioner’s sugar. Serve the tart on the day it was baked; do not refrigerate.