Heat oven to 350°F. In large bowl, combine all cake ingredients at low speed until moistened; beat 2 minutes at high speed.
Pour into ungreased 9x5-inch loaf pan. Bake at 350 for 25-35 minutes until crust is deep golden brown and cracks on top appear dry.
Meanwhile, in large saucepan combine rhubarb and 2 tbsp water; bring to a boil. reduce heat; cover and simmer 10 to 20 minutes until rhubarb is tender, stirring occaasionally. Stir in sugar. Cook 3 to minutes until sugar dissolves, stirring occasionally.
Cool cake completely in pan tipped on side on cooling rack. Remove from pan. For ease in cutting, slice loaf with bottom side up. To serve, spoon 2 tbsp sauce over each slice of cake. Serve with whipped topping, if desired.