Rhubarb Magic Cake

Why I Love This Recipe
It's gotta be magic when you dump a cup of boiling water over the top of your ingredients right before baking - and it turns into cake.
This recipe came from Mrs.George. She & my Mother were very good friends while we lived in Ill. Mr. & Mrs. George later moved to West Tennessee, where they both died.
Ingredients You'll Need
4 1/2 cups of 1/2 inch slices rhubarb
2 cups flour
1 1/2 cups sugar
2 teaspoons baking powder
1/2 teaspoon salt
6 Tablespoons melted butter
2/3 cup milk
1 teaspoon vanilla
1 egg
Topping:
1 cup sugar
1 Tablespoon cornstarch
1/2 teaspoon cinnamon
1 1/4 cup boiling water
Directions
Preheat the oven to 350 F.
Lightly grease a 9 x 13 inch pan.
Scatter rhubarb evenly into pan.
Sift together flour, 1 1/2 cups sugar, baking powder and salt.
Beat in melted butter, milk and vanilla.
Beat in the egg.
Batter will be quite thick.
Drop batter over rhubarb by heaping Tablespoons, then gently spread to fill pan.
For the topping, combine 1 cup sugar, cornstarch and cinnamon.
Sprinkle evenly over batter.
Gently pour the boiling water (here's the magic part!!) over all.
Bake about 50 minutes or until a toothpick inserted into the batter part comes out clean.
Enjoy with vanilla ice cream or whipped cream on top!