Directions Roll dough into a 1/8-inch circle on a floured surface and place in a 9-inch pie plate. Cut crust 1/2 in. beyond plate rim; flute edge. Chill 30 minutes. Preheat oven to 425°.
Foil pie crust twice. Use pie weights, dried beans, or uncooked rice. Bake 20–25 minutes on a lower oven rack until edges are golden brown. Remove foil and weights; bake 4 minutes until bottom is golden brown. Wire-rack cool.
In a large pot, mix sugar and cornstarch. Smoothly mix grapefruit juice and water. Heat and whisk over medium-high until thickened and bubbling. Continue cooking and stirring 2 minutes on low.
Get off the heat. Mix egg yolks with 1/2 cup hot filling and return to pan, stirring frequently. Gently boil and stir for 2 minutes. Get off the heat. Gently mix butter and extract. Pour hot filling into crust.
Beat egg whites and cream of tartar on medium speed in a large bowl until soft peaks form. Mix in sugar, 1 tablespoon at a time, on high until stiff glossy peaks form and sugar dissolves. Cover hot filling and seal edges to crust.
Bake meringue at 350° for 12–15 minutes until golden brown. Cool on wire rack for 1 hour. Serve after 3 hours of refrigeration. Save leftovers in the fridge.
Nutritional Info 1 piece: 433 calories, 16g fat (10g saturated fat), 107mg cholesterol, 204mg sodium, 68g carbohydrate (48g sugars, 1g fiber), 5g protein.