I give instructions here for making the crust quickly with your fingertips. If you’re more comfortable and familiar making it in a food processor or have another favorite technique, by all means use that. The pie dough recipe yields enough for two pie crusts and you’ll only use one here, so freeze the other for a future pie you’re excited to try. Last, note that between the crust and filling, you’ll use 3 eggs total (although you’ll be doing some separating–see below). Please note, rest time for the pie crust isn’t indicated in the cook times above.
Adapted from: The Lee Brothers Charleston Kitchen
To make the crust: Whisk first four ingredients together in a medium bowl. Using your fingertips, rub in butter until coarse meal forms and some small lumps remain. Drizzle vanilla extract over the dough and slowly sprinkle in cold water, 1 tablespoon at a time, quickly stirring with a fork or your fingers until the dough becomes sticky and begins to clump together into a more uniform mass. Divide dough into half and form 2 single flat, chubby disks; wrap each in plastic wrap and refrigerate for at least 1 hour and up to 1 day. Once chilled, roll out the dough on a lightly floured surface until it is large enough to fill a 9-inch pie plate. Carefully transfer the dough to the pie plate and nestle into place. Leave 1-inch of overhang (if there’s a great deal of overhang, trim), then fold edges of the dough under and crimp.
Pre-bake the crust: To avoid a soggy pie, prebake the crust on 400 F: Using a fork, lightly prick the bottom of the crust. Take a sheet of aluminum foil and layer it on top of the pie crust, gently nudging it down so it’s snug on the bottom and the sides. Fill the foil-covered crust with dried beans or pie weights to hold it in place. Bake for 15 minutes. Remove from the oven and remove pie weights/beans and foil. Brush crust with egg yolk to create a moisture seal (again, to prevent sogginess). Decrease the oven to 350 F, and place back in the oven to dry out further, another 5 minutes.
Make the filling: Finely grate the zest of one of the grapefruits (about 1 teaspoon loosely grated zest), and set aside. Segment the grapefruits: trim off the top and bottom so each end is flat. Peel the fruit by placing the tip of a sharp knife just inside the border where the pith meets the pulp and slicing down along the curvature of the fruit. Repeat until whole fruit’s been peeled. Then, over a bowl to catch the juice, gently cut the segments of pulp with a sharp knife by slicing towards the core as close as possible to the membranes that separate the segments. Preserve the juice. Gently strain the segments, reserving the segments and juice separately (you should have about 1 cup segments and 1/3 cup juice). Whisk the zest and salt into the grapefruit juice.
In a large bowl, whisk the egg whites and yolks together until they’re light and creamy in color, then whisk in the cream and melted butter.
In a medium bowl, mix the sugar, flour and cornmeal together. Add the dry ingredients to the egg mixture in thirds, whisking after each addition. Stir in the grapefruit juice until combined.
Pour the filling into the pie crust. Arrange the grapefruit segments in the custard (they’ll float to the surface as they bake). Transfer the pie to the oven and bake at 350 F until the top has nicely browned and the center jiggles stiffly, 35-45 minutes. Cool completely on a rack, about 20 minutes, before serving.