For Sweet Pastry Dough:
- 150 g all-purpose flour
- 1 1/2 tablespoons sugar
- 1/4 teaspoon salt
- 7 tablespoons cold unsalted butter, cut into bits
- 1 large egg yolk
- 1/2 teaspoon vanilla
- 1/2 teaspoon fresh lemon juice
- 2 1/2 tablespoons cold water
- 4 Florida grapefruit (preferably 2 pink and 2 red)
- 225 g mascarpone cheese* at room temperature
- 3 tablespoons finely chopped candied ginger
- 4 tablespoons icing sugar
- 23 to 25-centimetre round tart pan (3 centimetres deep) with removable bottom
- Pie weights or raw rice
Whisk together flour, sugar, and salt in a large bowl.Blend together flour and butter with your fingertips or a pastry blender until most of mixture resembles coarse meal with small (roughly pea-sized) butter lumps.Beat together yolk, vanilla, lemon juice, and water with a fork and stir into flour with fork until combined well.Gently knead with floured hands in bowl until a dough forms.Turn dough out onto a floured surface and gently knead 4 or 5 times.
Form dough into a ball, then flatten into a disc and chill, wrapped in cling film, for at least 1 hour and up to 2 days.Makes enough dough for a 23 to 25-centimetre tart.
Roll out dough with a floured rolling pin into a 33-centimetre round on a floured surface and fit into tart pan (if pastry breaks, press together with your fingers).Trim excess dough, leaving a ¨ö-inch overhang, then fold overhang inward and press against side of pan to reinforce edge.Lightly prick bottom of shell all over with a fork.Chill for 30 minutes.Preheat oven to 190 degrees Celsius. Line shell with foil and fill with pie weights.Bake in middle of oven for 10 minutes, then carefully remove foil and weights and bake shell until golden (13 to 15 minutes more).Transfer shell in pan to rack to cool.
Cut peel, including all white pith, from fruit with a sharp paring knife, then cut segments free from membranes and pat dry with paper towels.Squeeze 3 tablespoons of juice from membranes into a bowl.Whisk together mascarpone, candied ginger, 2 tablespoons of juice, and 2 tablespoons of icing sugar.Add remaining tablespoon of juice if mixture is too thick.Spread ginger mascarpone evenly in tart shell and top decoratively with fruit.Dust with remaining 2 tablespoons of icing sugar and serve immediately.