Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C). Butter a 9x13 inch baking dish. Jake Sternquist / Food Styling: Holly Dreesman / Prop Styling: Gabriel Greco
Spread rhubarb evenly in the bottom of the prepared baking dish. Jake Sternquist / Food Styling: Holly Dreesman / Prop Styling: Gabriel Greco
Sprinkle sugar over rhubarb, followed by gelatin mix, and finally cake mix. Pour water and melted butter over the top. Do not stir. Jake Sternquist / Food Styling: Holly Dreesman / Prop Styling: Gabriel Greco
Bake in the preheated oven until rhubarb is tender, about 45 minutes. Jake Sternquist / Food Styling: Holly Dreesman / Prop Styling: Gabriel Greco
Aunt Kaye's Rhubarb Dump Cake · Dinner Match Lab | Dinner Match Lab