Preheat oven to 350 degrees. Grease and flour a 9x13 inch baking dish.
In a large bowl, stir together oil and sugar, making sure they are well blended. Add egg, baking soda, flour, salt, and vanilla. Blend in sour cream until smooth. Fold in the cut up rhubarb or other fruit. Pour into prepared baking dish, spreading evenly.
In a seperate bowl mix together walnuts, sugar, and cinnamon until well combined. Sprinkly on top of the cake before baking, or halfway through the process.
Bake in the preheated oven until a toothpick inserted in the center comes out clean, about 40 minutes.
Notes
Great recipe that can utilize other fruit besides rhubarb as well.