Cream butter, sugar, vanilla, and salt. Mix in flour and rolled oats. Blend until dough is formed.
Press dough over bottom and sides of 9" pie plate, making a high, even edge. Chill.
Mix salt, sugar, and flour. Set aside.
Combine rhubarb & water in a saucepan. Cover and bring to a boil. Stir in sugar mixture. Boil, stirring often.
Fold a small amount of hot mixture into egg yolks. Stir eggs into hot mixture slowly. Pour into crust. Bake at 375 degrees for 25 minutes or until set.
Beat whites and salt until soft peaks form. Add sugar gradually. Beat until glossy. Beat in extracts.
Spread over the hot filling so that it touches the edge of the crust. Return to oven and brown for 8-10 minutes.