Adopted from Bon Appétit Magazine, January 2002, on Epicurious.com
For the grapefruit curd & garnish:
about 4 large red grapefruits
1 Tbl finely grated grapefruit zest (make sure to collect before slicing the grapefruits!)
1/3 cup plus 1/4 cup fresh grapefruit juice (collected while slicing the grapefruit segments)
1/3 cup fresh lemon juice (from about 2 to 3 lemons)
1 1/4 cups sugar
6 large eggs
2 large egg yolks
1 stick butter, sliced into 8 pieces, room temperature
a few drops of red food coloring
3/4 tsp unflavored gelatin
For the tart shell:
1 1/2 cups all-purpose flour
2 Tbl sugar
1/4 tsp salt
1 stick butter, sliced into 1/4-inch cubes, cold
3 Tbl heavy cream, cold
1 Tbl Grand Marnier (optional – otherwise, sub in 1 Tbl more cream)
1 large egg yolk
First, zest the grapefruit, reserving 1 tablespoon to use later. Then, with a sharp knife, slice off the top and bottom ends of each grapefruit. Rest the fruit on a cutting board, and slice from top to bottom down the sides, removing the skin and the white pith that lies beneath. Continue to slice away the skin, around the entire fruit. Cut away any pith you may have missed. Hold the peeled fruit over a bowl. Slice towards the core, as close as possible to the white membrane separating the segments. Make the same slice on the opposite side of the same segment. When the two cuts meet at the bottom, the citrus segment with slide out, and fall into the bowl. Repeat with the remaining segments. When done with the entire fruit, squeeze the juice into the bowl. Repeat with the remaining grapefruits. Then strain the juice into a separate container. Reserve 1/3 cup plus 1/4 cup of the grapefruit juice and all of the grapefruit segments, refrigerated in separate air-tight containers, until ready to use.
In a medium-sized, metal mixing bowl, whisk to combine the grapefruit zest, 1/3 cup grapefruit juice, lemon juice, sugar, eggs and egg yolks. Set the bowl over a saucepot filled with about 1-inch of gently simmering water. Add the butter, then whisk constantly until the sauce thickens and a thermometer inserted into the sauce registers 175°F, about 12 minutes. Be sure not to let the sauce boil, or go about the 175°F. Remove the bowl from above the water, then add a few drops of red food coloring, 1 drop at a time and stirring well between drops, to achieve a rosy shade of pinkish-orange. Be very careful – It’s a fine line between grapefruit pink and Pepto Bismol pink! Cool the sauce for about a half hour at room temperature, stirring occasionally. Cover with plastic, then chill in the refrigerator until cold, about 2 hours.
While the sauce cools, make the pastry shell: Combine the flour, sugar and salt in the bowl of an electric stand mixer fitted with the paddle attachment. (You can also use a hand-held electric mixer.) Blend on medium speed until combined. Then add the butter and blend on medium until the mixture resembles coarse crumbs, about 1 to 2 minutes or so. Add the cream, Grand Marnier and egg yolk, then blend on medium speed until the dough begins to clump together, about 1 minute or so. Gather the dough into a ball, flatten into a disk, then roll out the dough on a lightly floured work surface, forming a 13-inch round circle. Transfer the dough to a 10-inch diameter tart pan with a removable bottom. Fold the overhand in to form double-thick sides, then press onto the pan sides. Using a fork, pierce all over the bottom of the crust. Freeze for 30 minutes.
Pre-heat the oven to 350 F and arrange a rack in the middle position. Bake until the crust is lightly golden, about 30 minutes. Cool completely in the pan on a wire rack.
It helps to reinforce the grapefruit sauce a bit with gelatin: Place the remaining 1/4 cup grapefruit juice in a small sauce pot. Sprinkle the gelatin evenly over the surface of the juice and allow it to stand for 10 minutes. Then place the pot over medium-low heat and melt the gelatin mixture, stirring constantly. Add the gelatin mixture to the grapefruit sauce and whisk to combine.
Pour the grapefruit sauce into the cooled crust, then place in the refrigerator until set, about 2 hours. Cover lightly with plastic wrap and refrigerate until needed, up to 1 day.
Arrange the sliced grapefruit segments in concentric rings around the tart, staring with an outer layer and working your way in. I was able to get in two rows, but if you use smaller grapefruits, you may be able to fit three. Once you’ve topped the tart with the grapefruit slices, serve within 4 hours.