Step 1: Prepare the Baking Pan and Preheat the Oven
Start by preheating your oven to 350 degrees F (175 degrees C).
While the oven is heating up, grease and flour a 9×13-inch baking pan to ensure the cake doesn’t stick and will come out easily after baking.

Step 2: Mix the Cake Batter
In a large bowl, combine the cake mix, water, eggs, and oil.
Use an electric mixer on low speed to blend the ingredients until they are just moistened.
Then, increase the speed to medium and beat for 2 more minutes to create a smooth batter.
Pour the prepared batter into your greased and floured baking pan.

Step 3: Add the Rhubarb and Cream Topping
In a separate bowl, mix together the rhubarb and sugar.
Once combined, spoon this mixture evenly over the cake batter in the pan.
Finally, drizzle whipping cream over the top of the rhubarb and cake batter, distributing it as evenly as possible to ensure all areas get some delicious creaminess.

Step 4: Bake the Cake
Place the pan in your preheated oven and bake for approximately 40 minutes.
The cake is done when a toothpick inserted into the center comes out clean.
This is a good indication that the cake is fully baked through.

Step 5: Cool and Serve
After baking, allow the cake to cool completely in the pan.
Once cooled, carefully turn the cake out onto a serving dish for presentation.