Preheat the oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch baking dish.
1 1/4 cups white sugar
1 teaspoon baking soda
1/2 teaspoon salt
2 cups all-purpose flour
2 eggs, beaten
1 cup sour cream (we used greek yogurt) sometimes you need to add 1/2 cup more.
Once it is nice and smooth add in
3 cups diced rhubarb
In separate bowl mix together
1 cup white sugar
1/4 cup butter, softened
1/4 cup all-purpose flour
Sprinkle the mixture on top of the cake then dust lightly with ground cinnamon.
Bake in the preheated oven until a toothpick inserted in the center comes out clean, about 45 minutes.