This easy Rhubarb Dump Cake recipe features a homemade filling of tart, fresh rhubarb that transforms a box of vanilla cake mix into a simple dessert that’s truly special.
Consider this Rhubarb Dump Cake recipe semi-homemade — while traditional dump cakes combine the conveniences of a box of cake mix and canned pie filling, this one incorporates a fresh rhubarb filling that’s made from scratch. I much prefer fresh fillings, but I’ve never seen rhubarb in a can at the store anyway. Plus, many rhubarb dump cakes add strawberry Jello for sweet flavor and thickening…which I’m not a fan of either! Like my Rhubarb Bread and Rhubarb Coffee Cake recipes, the 100% fresh rhubarb gives this dump cake a lovely tartness that rhubarb fans clamor for!
Why This Is *the* Dump Cake to Make Right Now
Friends, rhubarb season is fleeting, so I’m going to gently push you to add this to your menu ASAP. Here’s what makes it a favorite:
- Tastes like homemade. As I mentioned, the typical cake-mix-and-canned-pie-filling dump cake equation just isn’t for me. For example, when I make Blueberry Dump Cake, I jazz-up the canned blueberry filling by adding fresh berries and lemon. And here, I go all-in with a homemade rhubarb-only filling (no Jello!), which makes this recipe taste like it was made from scratch, even though you’re still using a boxed mix!
- Easy to make. The genius behind dump cake is that you simply dump all the ingredients into a baking pan. Rhubarb filling first, which gets mixed right in the pan, followed by the cake mixture. (While some recipes have you sprinkling the dry cake mix over the filling and then drizzling it with melted butter, I combine the cake mix and butter first, and then sprinkle it over the filling. This gives a more consistent cake texture.)
- A dessert for rhubarb lovers. Rhubarb often gets paired with strawberries since they’re in season at the same time of year – and while I adore Strawberry Rhubarb Bars and Strawberry Rhubarb Freezer Jam, I also appreciate recipes where tart rhubarb takes on a solo feature. This rhubarb dump cake recipe is ALL about the rhubarb!
What You’ll Need
Scroll down to the printable recipe card to find the exact ingredient quantities and recipe instructions. You really don’t need all that much to make this rhubarb dump cake!
Rhubarb Filling:
- Rhubarb – Use fresh rhubarb stalks with a bright, deep red color for the prettiest dessert. If all you can find is mature green rhubarb, go ahead and use that – it’ll still taste the same. Learn more: Rhubarb 101.
- Lemon juice – Freshly squeezed lemon juice, not bottled.
- Sugar – To balance the tartness of rhubarb.
- Cornstarch – To thicken the filling.
Cake Layer:
- Cake mix – I use Duncan Hines Signature Perfectly Moist French Vanilla, but another vanilla cake mix you like will work too.
- Butter – You can use salted or unsalted butter. If you use unsalted butter, toss a couple pinches of salt into the cake mix mixture.
- Sanding sugar – For some sparkle and light crunch.
How to Make Rhubarb Dump Cake
You need only a few minutes to assemble this recipe. Here’s what you need to do.
- Make the filling. Stir together the rhubarb and lemon juice in a 9″ x 13″ baking dish, then fold in the sugar and cornstarch. Spread it into an even layer.
- Make the cake topping. Stir together the cake mix and melted butter in a mixing bowl.
- Finish assembling. Crumble the cake batter mixture over the rhubarb. Sprinkle the sanding sugar over the top.
- Bake. Place the pan in a 350º F oven and bake for 45-50 minutes, or until the rhubarb filling is thickened and bubbly, and the topping is golden brown. Remove from oven and let cool on a cooling rack.
How to Serve
We like to let this dessert cool for 20 to 30 minutes before serving, so it’s still beautifully warm. And we always enjoy it with vanilla ice cream, although you could certainly add a big dollop of whipped cream.
You can also eat it after it’s fully cooled. It’s really best enjoyed on the same day you bake it, but it’s totally fine to bake it earlier in the day and serve it later (great for entertaining).
Variations
Here are a couple ways you can change up this recipe:
- Try another cake flavor. Yellow, white, and lemon cake mixes would also work well with the flavor of the rhubarb filling.
- Add nuts. For added crunch and flavor, mix chopped, roasted walnuts or pecans into the cake batter before sprinkling it over the top.
How to Store
- Room temperature: You can make this rhubarb dump cake up to 8 hours in advance and store it at room temperature, uncovered.
- Refrigerator: After 8 hours at room temperature, you’ll want to refrigerate any remaining cake. Cover the baking dish with a tight-fitting lid or foil and store for up to 4 days.
More Rhubarb Recipes
Rhubarb Dump Cake
Ingredients
Rhubarb Filling
- 6 cups ½"-chopped fresh rhubarb (look for stalks with bright/deep red color)
- 1 tablespoon freshly squeezed lemon juice
- 1 cup granulated sugar
- ¼ cup cornstarch
Cake Layer
- 1 box (15.25 ounces) vanilla cake mix (I use Duncan Hines Signature Perfectly Moist French Vanilla)
- ¾ cup (1½ sticks) salted butter, melted
- 2 tablespoons coarse sanding sugar
Instructions
- Adjust oven rack to center of oven and preheat oven to 350°F.
Rhubarb Filling
- Add chopped rhubarb to a 9" x 13" baking dish. Sprinkle lemon juice evenly over the rhubarb, then fold a few times to incorporate. Spread rhubarb into an even layer.
- Sprinkle sugar evenly over rhubarb, then do the same with the cornstarch. Fold a few times to evenly incorporate. Spread rhubarb into an even layer. With a paper towel, wipe interior sides of baking dish for a cleaner finished appearance.
Cake Layer
- Add dry cake mix to a medium mixing bowl. Drizzle melted butter over the top, then stir to evenly combine.
- Using your fingers, crumble cake batter mixture into ¼" to ½" crumbles. Sprinkle crumbles evenly over top of rhubarb, leaving about 1" of exposed rhubarb filling around the perimeter of the baking dish. Do not press on or smooth out the cake batter crumbles.
- Sprinkle coarse sugar evenly over the cake batter crumbles.
- Bake 45-50 minutes, or until rhubarb is lightly thickened, glossy, and bubbling, and the cake batter topping is lightly browned.
- This easy dessert is best enjoyed on the day it is made, although it keeps perfectly well if you want to make it 6-8 hours in advance >> I recommend that you not cover the pan; just let it sit at room temperature uncovered. Our family especially likes to eat this while it's still a bit warm, about 20-30 minutes after it comes out of the oven – and with scoops of vanilla ice cream, of course!
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