Recipe Submitted by S. Campbell of Montana!
Combine all the ingredients for the rhubarb (butter, rhubarb, sugar) in a large saucepan over medium heat and cook slowly until the rhubarb is tender.
Add filling ingredients to the rhubarb; cook until thickened, stirring frequently. Cool slightly and then pour into a baked pie shell.
For the meringue, beat egg whites with vanilla and cream of tartar until soft peaks form. Gradually add the sugar, beating until stiff and glossy peaks form and all sugar is dissolved.
Spread the meringue over the warm filling, sealing to the edge of the pastry. This helps prevent the meringue from shrinking.
Bake at 350 degrees Fahrenheit for 12 to 15 minutes or until meringue is golden. Cool.
Before cutting a meringue-topped pie, dip knife in water to avoid sticking. Enjoy!