Rhubarb Cake

From my Grandma Trombley

Cream together:
1/2 C brown sugar (packed)
1 C white sugar
1/2 C shortening

ADD: 2 eggs mix well
1 C water
1 tsp vanilla

Sift together & add the following to the above
1 tsp baking powder
1 tsp salt
2 C all purpose flour

Add 1 1/2 C finely chopped fresh rhubarb
Pour into a 9x13 cake pan, top with the following mixture
1/2 C brown sugar (packed)
1 1/2 tsp cinnamon
1/4-1/2 C chopped walnuts

Bake 40 minutes at 350 degrees