A creamy custard is the perfect foil for tangy rhubarb in this wonderful spring pie.
To make crust: Set oven rack at lowest level; preheat to 375 degrees F. Coat a 9-inch glass pie plate with cooking spray. Stir together 1 cup flour, 1 tablespoon sugar and salt in a medium bowl. Melt 1 tablespoon butter in a small saucepan over low heat, swirling it in the pan until light brown, about 30 seconds. Pour into a small bowl and let cool. Stir in oil.
Slowly stir the butter-oil mixture into the flour with a fork until the mixture is crumbly. Gradually stir in enough ice water so that the dough will hold together. Press the dough into a flattened disk.
Place two sheets of plastic wrap overlapping by 2 inches on the work surface. Place pastry in the center and cover with two more overlapping sheets of plastic wrap. Roll the dough into a circle about 12 inches in diameter. Remove the top sheets and invert the dough over the prepared pie plate. Carefully peel away the remaining plastic wrap. Fold the edges under at the rim and crimp. Chill the pastry while you prepare the filling.
To make filling: Beat together 3/4 cup sugar and 1 tablespoon butter in a medium bowl until fluffy. Beat in egg, 2 egg whites, milk and vanilla until well blended. Toss rhubarb and 2 tablespoons flour in another bowl. Stir the rhubarb into the egg mixture. Turn the filling into the crust-lined pan, spreading evenly. Bake until the filling is firm, about 1 1/4 hours. Let cool to room temperature before adding meringue.
To make meringue: Position rack in the center of the oven; preheat to 375 degrees F. Beat 3 egg whites in a large mixing bowl with an electric mixer on medium speed until frothy. Add cream of tartar and beat on high speed just until soft peaks form. While continuing to beat egg whites, gradually add 1/2 cup sugar. Beat until stiff and glossy.
Spread the meringue over the pie filling, making sure that it touches the edge of the crust all the way around. Bake until the top is lightly browned, 12 to 15 minutes. Let cool on a rack for 1 hour before serving.
3 other carbohydrate, 2 fat