3/4cupgrapefruit juicefrom one large or two medium grapefruit
zest of one grapefruit
1 1/4cupsboiling water
For the meringue layer:
4egg whitesat room temperature
1tspvanilla extract or vanilla bean paste
To make the grapefruit filling:
Combine all of the ingredients except for the boiling water in a medium saucepan, and whisk until the corn starch fully dissolves. Add the boiling water and whisk everything together, then place the pan over medium-high heat.
Stir constantly with a rubber spatula, scraping down the bottom of the pan so that it doesn’t scorch. Bring the mixture to a slow boil, always stirring, until it thickens. You’ll notice that it goes from runny to thick in an instant. As soon as it thickens, remove the pan from the heat, whisk it to smooth out any lumps, and pour it into the baked and cooled pie shell. Spread it into an even layer. Press a layer of cling wrap on top, and let it cool to room temperature before refrigerating it to cool completely.
To make the meringue layer:
Combine the water, sugar, and corn syrup in a small saucepan over medium-high heat. Stir until the sugar dissolves, then brush down the sides of the pan with a wet pastry brush to prevent sugar crystals from forming. Once the sugar syrup comes to a boil, insert a candy thermometer and cook the syrup, without stirring, until it reaches 240 degrees Fahrenheit (115 C) on the thermometer.
While the sugar syrup is cooking, prepare the egg whites. Once the syrup reaches about 225 F, pour the room temperature egg whites into the clean bowl of a large stand mixer. Begin whipping them with the whisk attachment on medium speed. The goal is to have the white reach firm peaks at the same time the sugar syrup reaches 240 F. If the whites are ready first, stop the mixer—do not overbeat them!
When the sugar syrup is at 240, remove the pan from the heat. With the mixer running, carefully pour the hot syrup into the egg whites in a slow, steady stream. (If your saucepan does not have a spout, it might help to first transfer it to a large measuring cup with a spout before doing this step.) Turn the mixer to medium-high and beat until the whites are glossy, voluminous, and hold firm peaks. Add the vanilla extract and beat to combine.
Spread or pipe the meringue onto the cooled pie filling. You can eat it as-is, or use a kitchen torch to toast the top of the meringue. Serve immediately, and store leftovers in the refrigerator for up to 3 days. Although it will keep, this pie is best on the day that it’s made.
I tried something new (to me) with the meringue layer this time—instead of making a plain meringue with egg whites and sugar, I made an Italian meringue by boiling sugar and water, then adding it to the egg whites. It’s less traditional, but I was trying to prevent the common problem of the meringue “weeping” into the pie, and Italian meringue is more sturdy. I really liked this change! It doesn’t have quite the same airy texture (it’s a bit more like a marshmallow texture) but it held up much better. For once I didn’t feel like I had to rush my meringue pie to the table before it deflated or wept. One more thing: the filling has quite a bit of corn starch, which helps it slice beautifully and remain stable once sliced. If you like your pies to have a softer, more fluid filling, and don’t mind a little slip-sliding around the plate, consider reducing the corn starch to 1/3 cup.