Rhubarb Dump Cake
This rhubarb dump cake is the ultimate easy dessert — made with just a few simple ingredients layered in one pan. Tart rhubarb bakes into a jammy filling under a golden, buttery cake topping for a comforting treat ready in under an hour.
Equipment
- 9x13 inch baking dish
- mixing bowl
- measuring cups
- spoon or spatula
Ingredients
- 4 cups rhubarb, sliced
- 1 cup granulated sugar
- 1–2 tbsp cornstarch
- 1 box (15 oz) yellow cake mix
- 1/2 cup butter, melted
- 1 cup warm water
Instructions
- Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish with non-stick spray.
- In a bowl, toss the sliced rhubarb with the granulated sugar and cornstarch until evenly coated. Let sit for 5 minutes.
- Spread the rhubarb mixture evenly across the bottom of the prepared baking dish.
- Sprinkle the dry cake mix evenly over the rhubarb in a single layer. Do not stir.
- In a small bowl, mix melted butter with warm water. Pour evenly over the cake mix, covering as much surface as possible.
- Bake uncovered for 40–55 minutes, until the top is golden brown and the filling is bubbling at the edges.
- Remove from the oven and let rest for at least 15 minutes before serving.
- Serve warm with vanilla ice cream or whipped cream if desired.
Notes
Add 1–2 tablespoons of cornstarch to prevent a watery filling. For best results, mix melted butter with water before pouring over the cake mix to avoid dry patches. Let the cake rest at least 15 minutes before serving for a thicker texture.