4tablespoonsstrained blood orange juice (optional, for color - otherwise, 4 more tablespoons grapefruit juice)
4tablespoonsSt. Germain Elderflower Liqueur
2-3teaspoonsfinely grated grapefruit zest (colorful part only, from 1 medium grapefruit)
Have a rack positioned in the lower third of the oven and preheat the oven to 400º. Have your pie shell baking on a rimmed baking sheet on the bottom rack, and blind-bake it until it's golden all over, somewhere between par-baked and fully-baked. The gluten-free crust won't brown much more once the custard is added. (If your pie crust has already baked and cooled, that's fine – put it in the oven for 5 minutes before pouring in the custard.)
Make the custard:
In a large bowl, whisk together the flour, sugar, and salt. Whisk in the eggs one at a time, whisking until combined after each addition. Whisk in the melted butter, then the grapefruit and blood orange juices, and finally the heavy cream and St. Germain liqueur. The mixture should thicken up with the addition of the cream. Strain the mixture into a large measuring pitcher or bowl, and whisk in the grapefruit zest to distribute it evenly.
Bake the pie:
Pour the custard into the hot pie shell set on a rimmed baking sheet. Carefully transfer to the lower rack of the oven, reduce the temperature to 325ºF, and bake until the sides are slightly puffed and the center is quite wobbly but not watery, about 35-45 minutes. Be careful not to over-bake, or the filling will separate.
Remove the pie from the oven and cool completely, 2-3 hours; it will still be cooking from residual heat. (If the filling is too soft to slice, chill the pie 1-2 hours.) The pie will keep at room temperature for one day, or refrigerated for up to three days, though it is best on the day of baking when the crust is most crisp.
Inspired by and adapted from The Four and Twenty Blackbirds Pie Book.I highly recommend investing in a bottle of St. Germain to make this pie. The alcohol all cooks out, but it amplifies the floral flavor of the grapefruit and makes the pie taste magical. (As a bonus, you'll then be able to make the best cocktail ever, the Pink Grapefruit Vieux Mot, invented by my friend Calvaleigh, or splash it into prosecco or white sangrìa.) Lacking St. Germain, you could try substituting an orange or ginger liqueur, or simply omitting the liqueur and adding another quarter cup of sugar to the filling.I made this with my gluten-free pie dough, but if gluten isn't an issue for you, feel free to use your favorite pie crust (or half a recipe of my flakiest, all-butter pie dough) and use all-purpose flour in place of the rice flour in the filling. Having the pie crust hot when you add the filling helps to keep the crust crisp. My gluten-free crust worked best when I blind-baked it almost all the way, until golden all over; it didn't brown much more once the filling was added. This pie is best the day that it's baked, but can be refrigerated for up to three days.All ounce measurements are by weight.Nutritional values are based on one of eight servings.