- In a bowl, combine the flour, sugar and salt. Using your fingertips, incorporate the butter into the flour until flaky. Gradually add the water and combine just until the dry ingredients are moistened, making sure to leave pieces of butter intact. The dough will be soft and sticky.
- On a floured work surface, roll the dough out to form a 10 x 6-inch (25 x 15 cm) rectangle. Using a pastry brush, remove any excess flour. Fold the dough in 3 widthwise. Fold the dough in half lengthwise to form a square. Cover with plastic wrap. Refrigerate for 30 minutes.
- On a floured work surface, roll the dough out to form an 11-inch (28 cm) circle. Add more flour as needed. Line a 9-inch (23 cm) tart pan with removable bottom with the dough. Prick all over with a fork. Refrigerate for 30 minutes.
- With the rack in the middle position, preheat the oven to 400°F (200°C).
- Cover the dough with a sheet of foil and fill with dried beans or ceramic pie weights. Bake for 25 minutes. Remove the beans and foil. Bake for another 15 minutes or until the crust is golden. Let cool on a wire rack.
- In a pot, off the heat, whisk together the sugar, cornstarch and grapefruit zest. Add the eggs and egg yolks. Mix well. Add the water, grapefruit juice, lemon juice and salt. Bring to a boil over medium heat, stirring constantly and scraping the bottom and sides of the pot. Simmer for 1 minute. Strain through a sieve placed over a bowl, if desired. Add the butter and stir until melted.
- Pour the grapefruit cream into the cooled crust. Cover with plastic wrap directly on the surface of the cream. Let cool. Refrigerate for 4 hours or until completely chilled.
- In a small pot, bring the water, sugar and corn syrup to a boil. Simmer over medium heat until a candy thermometer reads 240°F (116°C).
- In a bowl, whisk the egg whites and vanilla with an electric mixer on medium speed until soft peaks form. Once the syrup reaches 240°F (116°C), reduce the speed of the mixer. Pour the hot syrup over the egg whites, avoiding the beaters. Increase the speed and continue to beat until the meringue cools and forms very stiff peaks.
- Transfer the meringue into a pastry bag fitted with a large plain tip. Pipe the meringue into small circles of varying sizes to completely cover the grapefruit cream (see note).
- Using a kitchen torch, brown the surface of the meringue (see note). Garnish with grapefruit zest, if desired.
You can replace the water with grapefruit juice for a more pronounced grapefruit taste and to accentuate the tartness in the filling. If you’d like a deeper red filling, you can also replace some of the water with blood oranges.
You can also spread the meringue in an even layer over the grapefruit cream using a spatula.
You can brown the meringue in the oven under the broiler for a few seconds.