In a saucepan, mix together the 3/4
cup sugar and cornstarch, and slowly pour in the hot water and butter,
stirring to dissolve any lumps.
Beat egg yolks lightly and add,
along with the sour orange juice. Stir constantly over medium-low
heat until the mixture has thickened and coats the spoon. Do not
boil. Carefully pour the filling into the baked pie shell.
For the meringue, beat the egg whites until frothy. Continue to
beat, gradually adding the 3 tablespoons sugar, until the beater
holds stiff peaks when lifted. Gently swirl the meringue over the
filling, making sure it touches the edges of the crust all the way