Step 1

On a floured surface, roll dough to a 1/8-in.-thick circle; transfer to a 9-in. pie plate. Trim crust to 1/2 in. beyond rim of plate; flute edge. Refrigerate 30 minutes. Preheat oven to 425°.

Step 2

Line pie crust with a double thickness of foil. Fill with pie weights, dried beans or uncooked rice. Bake on a lower oven rack until edges are golden brown, 20-25 minutes. Remove foil and weights; bake until bottom is golden brown, about 4 minutes. Cool on a wire rack.

Step 3

Meanwhile, in a large saucepan, combine the sugar and cornstarch. Stir in grapefruit juice and water until smooth. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir 1/2 cup of hot filling into egg yolks; return all to pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Remove from the heat. Gently stir in butter and extract. Pour hot filling into crust.

Step 4

In a large bowl, beat egg whites and cream of tartar on medium speed until soft peaks form. Gradually beat in sugar, 1 tablespoon at a time, on high until stiff glossy peaks form and sugar is dissolved. Spread evenly over hot filling, sealing edges to crust.

Step 5

Bake at 350° until the meringue is golden brown, 12-15 minutes. Cool on a wire rack for 1 hour. Refrigerate for at least 3 hours before serving. Store leftovers in the refrigerator.