Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9 inch round cake pan.
In a medium bowl, mix together the flour, 1/2 cup sugar, baking powder, and salt. Beat in the eggs, butter, and vanilla until smooth. Spread the batter into the prepared pan.
In a medium saucepan, combine the rhubarb, 2 tablespoons sugar and cornstarch. Cook and stir over medium heat until the rhubarb is tender. Spread the rhubarb over the batter in the pan.
In a medium glass or metal bowl, beat the egg whites until stiff peaks form. Gradually add 1/4 cup sugar, beating until the mixture is thick and glossy. Spread the meringue over the rhubarb layer.
Bake for 30 to 40 minutes in the preheated oven, until the top is golden brown. Allow to cool before serving.
Interesting Facts
Rhubarb is a member of the buckwheat family, and is native to Siberia.
Meringue is a type of dessert topping made with whipped egg whites and sugar.
German Rhubarb Meringue Cake is a popular traditional dessert in Germany.